WATER 


FG:R>:;MN;   .    . 


PURPOSES 


EXAMINATION  OF  WATER. 


LEFFMANN. 


BY  THE  SAME  AUTHOR. 


Sanitary  Relations  of  the  Coal-tar  Colors. 

BY  THEODORE  WEYL. 

AUTHORIZED     TRANSLATION. 

isrno.    154  pages.    $1.25. 


Analysis  of  Milk  and  Milk  Products. 

Fourth  Edition,  Revised  and  Enlarged. 
1 2 mo.    Illustrated.    120  pages.    $1.25. 


Select  Methods  in  Food  Analysis. 

BY  HENRY  LEFFMANN  AND  WILLIAM  BEAM. 
Second  Edition.    8vo.    396  pages.    $2.50. 


EXAMINATION  OF  WATER 


SANITARY  AND  TECHNIC  PURPOSES. 


BY 
HENRY  LEFFMANN,  A.M.,  M.D.,  PH.D., 

PROFESSOR   OF  CHEMISTRY  IN  THE  WOMAN'S  MEDICAL  COLLEGE  OF  PENNSYL- 
VANIA AND  IN  THE  WAGNER  FREE  INSTITUTE  OF  SCIENCE;  PRESIDENT 
OF  THE   ENGINEERS'  CLUB   OF  PHILADELPHIA    1901;    VICE- 
PRESIDENT  (BRITISH)  SOCIETY  OF  PUBLIC  ANALYSTS 
1901-02 


SEVENTH  EDITION,  REVISED  AND  ENLARGED,  WITH 
ILLUSTRATIONS. 


The  first  two  edition1:  of  this  work  were  P*  epared  and  issued 
under  the  joint  authorship  of  Henry  Lfffmann  end  William  Beam. 


PHILADELPHIA 

P.   BLAKISTON'S   SON   &  CO. 

1012  WALNUT  STREET 


COPYRIGHT,  1915,  BY  HENRY  LEFFMANN. 


' 


T  U  K    M  A  P  £.  B     PRBSS     YORK     PA 


I  DEDICATE  THIS  BOOK  TO  THE 
MEMORY   OF 

&g  flfcotbet, 

TO   WHOSE   WISE  PRECEPT  AND  EXAMPLE 

IN   MY  BABYHOOD 

I  OWE  WHATEVER  MERIT  MY  MANHOOD  YEARS 
MAY  SHOW. 


313149 


— If  thou  couldst,  doctor,  cast 
The  water  of  my  land. 


PREFACE. 

The  favor  with  which  this  work  was  received 
on  the  occasion  of  the  issuing  of  the  first  edition, 
and  the  continuing  sale  until  now  the  seventh 
edition  is  printed,  may  be  taken  as  evidence  that 
it  finds  an  appropriate  place  in  the  library  of  the 
chemist. 

This  edition  has  been  prepared  from  the  point 
of  view  of  former  editions,  namely,  to  furnish  the 
commercial  and  works-laboratory  with  a  summary 
of  the  best  processes  for  ascertaining  the  sanitary 
and  technical  value  of  a  water  sample. 

Notwithstanding  the  activity  among  bacteri- 
ologists, the  chemical  examination  of  water  still 
holds  a  prominent  and  important  place,  and  can- 
not be  neglected  in  any  field  of  sanitary  inquiry. 

The  present  edition  has  been  extensively  re- 
vised, and  the  procedures  brought  into  general 
agreement  with  those  recommended  by  the 
American  Public  Health  Association  (quoted  as 
APHA).  A  comparison  of  the  present  book  with 
the  first  edition  issued  under  the  joint  authorship 
of  Dr.  William  Beam  and  myself,  will  show  inter- 
esting changes,  notably  the  substitution  of  proc- 

ix 


X  PREFACE. 

esses  devised  by  American  workers  for  those  of 
foreign  origin. 

Among  the  additions  are  summaries  of  some 
of  the  later  researches  on  corrosion  of  metals  by 
water,  methods  of  bacteriologic  differentiation 
and  details  of  APHA  methods  of  determining 
color,  turbidity  and  hardness. 

It  has  seemed  premature  to  adopt  the  change  of 
expressions  for  common  metric  measurement, 
by  substituting  liter  and  mil  for  c.c.,  although 
I  favor  such  change  in  the  interest  of  accuracy 
and  precision.  The  error  involved  is  negligible 
in  the  class  of  procedures  given  in  this  book.  All 
temperatures  are  centigrade. 

H.  L. 
PHILADELPHIA. 


CONTENTS. 


NOTE  ON  WATER-SUPPLY xiii-xvi 

NATURAL  HISTORY  AND  CLASSIFICATION  OF  NATURAL 

WATERS 1-7 

ANALYTIC  OPERATIONS. 

Chemical  Examinations: 

Collection  and  Preliminary  Examination — 
Total  Solids — Chlorin — Nitrogen  in  Am- 
monium Compounds  and  Organic  Matter — 
Nitrogen  as  Nitrates — Nitrogen  as  Nitrites 
— Oxygen-consuming  Power — Phosphates — 
Dissolved  Oxygen — Poisonous  Metals — 
General  Quantitative  Analysis — Spectro- 
scopic  Analysis — Specific  Gravity — Action 
of  Water  on  Metals— Boiler  Waters.  .  .  .  8-88 

Biologic  Examinations 89-113 

INTERPRETATION  OF  RESULTS. 

Statements  of  Analysis — Sanitary  Applica- 
tions— Purification  of  Water — Identifica- 
tion of  Source  of  Water 114-136 

ANALYTIC  DATA. 

Factors  for  Calculation — Atomic  Weights  .    .  137-138 

INDEX 


XI 


NOTE  ON  WATER-SUPPLY. 

The  human  race  must  have  recognized  at  an 
early  period  the  value  of  an  abundant  supply  of 
pure  and  refreshing  water.  Pastoral  communities 
would  be  obliged  to  guide  their  movements  along 
lines  that  would  keep  them  within  convenient 
reach  of  streams  and  pools  for  watering  cattle; 
agricultural  nations  could  only  establish  them- 
selves where  water  was  abundant.  Of  the  two 
classes,  the  former  would  be  much  less  likely  to 
develop  soil-pollution,  and,  accordingly,  we  find 
that  it  is  with  agricultural  and  manufacturing 
centers — i.  e.,  towns  and  cities — that  the  serious 
difficulties  with  regard  to  water-supply  arise. 
Drainage  areas  are  easily  polluted;  in  all  the  civi- 
lized countries  the  streams  receive  more  or  less 
sewage,  and  are  correspondingly  offensive  to  the 
senses  and  dangerous  to  health.  The  subsoil 
is  better  adapted  to  deal  with  normal  pollution, 
but  its  powers  are  not  inexhaustible,  and  in  time 
wells  and  springs  become  unsafe.  The  usual 
course  of  events  in  this  matter  is  well  portrayed 
by  Sextus  Julius  Frontinus,  who  was  Water 
Commissioner  of  Rome  from  A.  D.  97  to  103,  and 
who  wrote  a  comprehensive  account  of  the 

xiii 


XIV  NOTE    ON   WATER-SUPPLY. 

water-supply  of  that  city.  He  says  that  from  the 
building  of  the  city  until  its  four  hundred  and 
forty-first  year  (312  B.  c.),  the  citizens  were  sup- 
plied with  water  from  the  Tiber,  or  from  wells  and 
springs.  These  springs,  as  with  other  nations  of 
antiquity,  were  often  credited  with  healing  powers, 
either  due  to  some  medicinal  ingredients  or  be- 
cause the  locality  was  supposed  to  be  the  abode 
of  a  minor  deity,  whose  favor  could  be  secured 
in  various  ways.  The  Roman  water-supply 
became  unsatisfactory;  aqueducts  were  built, 
and  these  supplied  the  city  for  centuries.  Two  of 
the  original  aqueducts  are  still  in  use,  supplying 
modern  Rome  with  excellent  water.  The  quan- 
tity of  water  supplied  to  the  ancient  city  during 
the  height  of  the  development  of  the  aqueduct 
system — the  early  part  of  the  second  century  of 
the  Christian  era — is  not  accurately  known,  but 
Clemens  Herschel,  after  careful  examination  of  all 
data,  fixes  it  at  about  50,000,000  gallons  a  day. 
Most  of  the  supply  was  of  good  quality,  but  some 
of  the  aqueducts  delivered  river  water  that  was 
frequently  turbid.  No  proper  filtering  basins 
were  in  use,  but  special  interrupting  chambers 
assisted  in  getting  rid  of  the  coarser  suspended 
matters. 

Much  less  is  known  of  the  water-supply  of  the 
other  great  cities  of  the  ancient  world.  Aristotle, 
in  his ' '  Constitution  of  Athens, ' '  refers  to  an  official 


NOTE    ON   WATER-SUPPLY.  XV 

designated  "Superintendent  of  Springs,"  which 
shows  that  municipal  hygiene  was  not  wholly 
overlooked  in  that  city.  Jerusalem,  during  its 
influential  period,  was  apparently  well  supplied 
with  water.  The  remains  of  underground  con- 
duits have  been  lately  discovered,  including  a 
tunnel  cut  through  rock  to  a  point  distant  about 
300  meters  in  a  direct  line,  but  an  actual  length 
much  greater  on  account  of  the  tortuous  course. 
This  tunnel  was  probably  executed  in  the  reign 
of  Hezekiah  (eighth  century  B.  c.).  An  inscrip- 
tion found  on  the  interior  wall  some  years  ago, 
states  that  the  tunnel  was  bored  from  each  end 
and  the  borers  met  nearly  in  line.  It  leads  from 
a  spring,  now  called  the  Virgin's  Spring  (consid- 
ered as  identical  with  the  ancient  Gihon),  to  a 
point  near  the  Pool  of  Siloam,  at  the  southeast 
corner  of  the  city. 

In  common  with  the  general  decline  of  intelli- 
gence and  morals  which  affected  Europe  during 
the  thousand  years  from  the  fifth  to  the  fifteenth 
century,  the  protection  of  the  water-supply  was 
but  little  regarded.  The  aqueducts  fell  into  dis- 
use, and  at  present  are  mostly  represented  by  a 
few  scattered  ruins  studied  only  by  the  antiquary 
and  historian. 

It  is  not  appropriate  to  discuss  the  engineering 
features  of  ancient  or  modern  water-supply,  but 
it  is  worth  while  to  correct  a  widespread  error  in 


XVI  NOTE    ON   WATER-SUPPLY. 

regard  to  the  Roman  engineers.  It  is  often  said 
that  they  did  not  know  that  water  will  rise  to  its 
original  level,  and,  therefore,  built  extensive 
aqueducts  to  carry  water  over  valleys.  The  fact 
is  that  they  were  as  fully  aware  of  the  principle  as 
modern  engineers,  but  it  was  usually  cheaper  for 
them  to  build  the  aqueducts  than  to  use  inverted 
siphons.  They  did  use  the  latter  at  times.  In 
the  first  century  of  the  Christian  era,  an  aqueduct 
for  supplying  Lyon  (Lugdunum)  was  provided 
with  a  series  of  seven  lead  pipes,  each  about  20 
centimeters  in  diameter,  to  carry  water  across  a 
deep  valley. 


NATURAL  HISTORY  AND  CLASSIFI- 
CATION OF  WATER. 

Pure  water  is  an  artificial  product.  Natural 
waters  always  contain  foreign  matters  in  solution 
and  suspension,  varying  from  mere  traces  to 
very  large  proportions.  The  properties,  effects, 
and  uses  of  water  are  considerably  modified  by 
these  ingredients,  and  the  object  of  analysis  is 
to  ascertain  their  character  and  amount.  Since 
these  are  largely  dependent  on  the  history  of  the 
water,  a  classification  based  on  this  will  be  con- 
venient. We  may  distinguish  four  classes  of 
natural  waters : 

Rain  Water. — Water  precipitated  from  the 
atmosphere  under  any  conditions,  and  therefore 
including  dew,  frost,  snow,  and  hail. 

Surface  Water. — All  collections  of  water  in 
free  contact  with  the  atmosphere,  as  in  streams, 
seas,  lakes,  or  ponds. 

Subsoil  or  Ground  Water. — Water  not  in  free 
contact  with  the  atmosphere,  percolating  or 
flowing  through  soil  or  rock  at  moderate  distance 
below  the  surface,  and  derived  in  large  part  from 
the  rain  or  surface  water  of  the  district. 

Deep  or  Artesian  Water. — Water  accumulated 


2  HISTORY    A'ND    CLASSIFICATION. 

at  considerable  depth  below  the  surface,  from 
which  the  subsoil  water  of  the  district  has  been 
excluded  by  difficultly  permeable  strata. 

Rain  water,  when  gathered  in  the  open  country 
and  in  the  later  period  of  a  prolonged  rain  or  snow, 
is  the  purest  form  of  natural  water.  When 
collected  directly,  it  contains  but  little  solid 
matter,  this  consisting  principally  of  ammonium 
compounds  and  particles  of  organic  matter,  living 
and  dead,  gathered  from  the  atmosphere.  In 
districts  near  the  sea  an  appreciable  amount  of 
chlorids  will  be  present.  It  is  obvious  that  a 
prolonged  rain  will  wash  out  the  air,  but  since 
storms  are  usually  attended  by  wind,  fresh  por- 
tions of  air  are  continually  flowing  in,  and  thus 
the  water  never  becomes  perfectly  pure.  Rain 
water  collected  in  inhabited  districts  is  usually 
quite  impure. 

Surface  Water. — Rain  water  in  part  flows  off 
on  the  surface,  and  gains  in  the  proportion  of 
suspended  and  dissolved  matters,  the  former 
being  found  in  large  amount  when  the  rainfall  is 
profuse.  The  wearing  action  of  water  is  depend- 
ent on  the  amount  and  character  of  these  sus- 
pended materials.  From  the  higher  levels  of  a 
watershed,  the  streams,  more  or  less  in  the  form 
of  torrents,  gather  into  larger  currents,  and, 
reaching  lower  levels,  become  slower  in  move- 
ment, and  deposit  much  of  the  suspended  matter. 


SUBSOIL   WATER.  3 

By  admixture  of  the  waters  from  widely  separated 
districts  the  character  and  amount  of  the  dis- 
solved matters  are  much  modified. 

It  is  obviously  impossible  to  establish  close 
standards  of  composition  for  surface  waters.  In 
the  case  of  rain  water,  falling  on  the  surface  of 
undisturbed,  unpopulated  territory,  the  amount 
of  solids  dissolved  will  be  small,  and  will  consist 
principally  of  carbonates  and  sulfates.  The 
water  of  lakes  and  rivers  is,  however,  in  part 
derived  from  springs,  which  may  proceed  from 
great  depths,  and  thus  introduce  substances  not 
easily  soluble  in  surface  water,  nor  derivable 
from  the  soil  of  the  district. 

The  exposure  to  light  and  air  which  surface 
water  undergoes,  results  in  the  absorption  of 
oxygen  and  loss  of  carbonic  acid,  together  with 
the  oxidation  of  the  organic  matter.  The  dimi- 
nution of  the  rapidity  of  the  current  permits  the 
deposition  of  the  suspended  matters,  and  this 
occurs  especially  as  the  river  approaches  the  sea, 
not  only  from  the  retarding  influence  of  the  tidal 
wave,  but  from  the  precipitating  action  of  the  salt 
water. 

Subsoil  Water. — Water  that  penetrates  the 
soil  passes  to  various  depths,  according  to  the 
porosity  and  arrangement  of  the  strata.  As  a 
rule,  it  descends  until  it  reaches  but  slightly  per- 
vious formations,  upon  the  level  of  which  it 


4  HISTORY   AND    CLASSIFICATION. 

accumulates.  In  the  upper  layer  of  soil  it  dis- 
solves mineral  and  organic  ingredients,  and  be- 
comes impregnated  with  microorganisms,  through 
the  agency  of  which  the  organic  matter  undergoes 
important  transformations.  The  water,  con- 
stantly accumulating,  gradually  flows  along  the 
incline  of  the  impervious  stratum,  or  through  its 
fissures,  and  may  either  pass  downward  or  emerge 
in  the  form  of  a  spring. 

Much  difference  is  observed  in  the  composition 
of  subsoil  waters,  but  as  a  general  rule  they  con- 
tain small  amounts  of  mineral  substances  and 
organic  matter.  In  populated  districts,  however, 
a  marked  change  is  produced  through  admixture 
with  water  containing  animal  and  vegetable 
products  in  various  stages  of  decomposition.  It 
is  especially  the  organic  matter  containing  nitro- 
gen that  is  of  importance.  These  are  mostly 
unstable,  and  decompose,  partly  by  oxidation, 
partly  by  splitting  up  into  simpler  forms ;  changes 
in  most  cases  brought  about  by  microorganisms. 
The  nitrogen  is  in  part  converted  into  ammonium 
compounds,  but  a  considerable  portion  suffers 
further  oxidation,  and  in  association  with  the 
mineral  substances  present  forms  nitrites  and 
nitrates,  especially  the  latter.  This  is  called 
"nitrification." 

Nitrification  takes  place  under  the  influence 
of  microbes,  the  habitat  of  which  does  not  extend 


DEEP    WATER.  5 

more  than  a  few  yards  below  the  surface  of  the 
soil.  Several  microorganisms  with  active  nitri- 
fying powers  have  been  isolated  and  described. 
The  nitrifying  action  is  often  exerted  upon  the 
ammonium  compounds  formed  from  the  organic 
matter.  The  presence  of  some  substance  capable 
of  neutralizing  acids  is  usually  necessary  to  con- 
tinuous action.  Calcium  and  magnesium  car- 
bonates fulfil  this  function.  Nitrates  are  the  final 
result  of  this  action;  nitrites  are  present  at  any 
given  time  only  in  small  quantity.  Denitrifica- 
tion — that  is,  the  reduction  of  nitrates  and  nitrites 
to  ammonium  compounds — takes  place  also  under 
the  influence  of  microbes,  and  is  especially  apt  to 
occur  when  considerable  quantities  of  decom- 
posing organic  matter  are  introduced.  Several 
species  of  denitrifying  bacilli  have  been  described. 
A  partial  reduction  sometimes  occurs,  and  a  not- 
able proportion  of  nitrites  is  found,  but  in  the  pres- 
ence of  actively  decomposing  organic  matter, 
such  as  that  in  sewage,  a  complete  reduction, 
even  to  the  liberation  of  nitrogen,  may  occur. 

Deep  Water. — Water  which  penetrates  the 
fissures  of  the  fundamental  rock-formations  may 
pass  to  great  depths,  and  by  following  the  lines  of 
the  lowest  and  least  permeable  strata  may  be 
transported  to  points  far  removed  from  those  at 
which  it  was  originally  collected.  The  chemical 
changes  thus  induced  include  most  of  those 


0  HISTORY    AND    CLASSIFICATION. 

which  take  place  at  higher  points,  but  the  increase 
of  pressure  and  temperature  confers  increased 
solvent  power.  Carbonic  acid  will  accumulate 
under  conditions  favorable  to  the  solution  of  cal- 
cium, magnesium,  and  iron  carbonates,  and  iron 
and  manganese  oxids  may  be  converted  into  car- 
bonates and  then  dissolved.  Sulfates  are  re- 
duced to  sulfids,  and  these  subsequently,  by  the 
action  of  carbonic  acid,  yield  hydrogen  sulfid. 
Organic  matter,  living  and  dead,  plays  an  impor- 
tant part,  determining  the  reduction  of  ferric 
compounds  to  ferrous,  and  of  the  sulf ates  to  sulfids, 
and  is  itself  converted  ultimately  into  ammonium 
compounds,  notable  quantities  of  which  are  often 
found  in  deep  waters.  Further,  it  is  found  that 
nitrates  and  nitrites  are  present  only  in  small 
amount,  except  from  certain  strata  rich  in  organic 
matter.  In  some  cases  the  water  acquires  very 
high  temperature,  and  dissociation  of  rocks  occurs 
with  solution  of  considerable  amounts  of  silicic 
acid,  which  is  ordinarily  but  sparingly  soluble 
in  water. 

Masses  of  water  thus  accumulated  under  heat 
and  pressure  may  find  their  way  to  the  surface 
either  through  natural  fissures  or  be  reached  by 
borings. 

While  no  absolute  unchangeable  line  can  be 
drawn  between  deep  and  subsoil  waters,  yet  it  will 
in  most  cases  be  found  that  the  deep  water  of  a 


DEEP    WATER.  7 

given  district,  whether  obtained  through  natural 
or  artificial  channels,  will  be  decidedly  different 
in  composition  from  the  subsoil  or  surface  water 
of  the  same,  and  that  the  rocks  passed  through 
in  such  cases  will  be  characterized  by  one  or  more 
strata,  difficultly  permeable  to  water,  and  there- 
fore preventing  direct  communication.  The  char- 
acteristic differences  between  surface,  subsoil, 
and  deep  waters  are  clearly  indicated  in  the  table 
of  analyses  given  in  the  appendix. 

The  fact  that  mere  depth  is  not  the  essential 
difference  between  the  two  classes  of  waters  is 
shown  by  comparison  between  the  composition  of 
the  water  (expressed  in  parts  per  million)  from 
a  well  at  Barren  Hill,  near  the  northern  border  of 
Philadelphia  County,  and  a  deep  well  at  Locust 
Point,  Baltimore.  The  former  is  a  dug  well,  130 
feet  deep;  the  latter  is  an  artesian  boring  of  128 
feet,  which  in  its  descent  passes  through  4  feet  of 
solid  rock.  The  deeper  well  is  evidently  supplied 
by  subsoil  water.  The  artesian  well,  though 
located  about  100  yards  from  a  brackish,  sewage- 
laden  estuary,  evidently  derives  no  water  from  it. 

BARREN  HILL         LOCUST  POINT 
WELL.  WELL. 

Total  solids,  .. 470.00  Less  than  100.00 

Chlorin, 1 20 .  oo  4.68 

Nitrogen  as  nitrates,       2  2  .  oo  none 


ANALYTIC  OPERATIONS. 

COLLECTION  AND  PRELIMINARY 
EXAMINATION  OF  SAMPLES. 

Great  care  must  be  taken  in  collecting  water 
samples,  in  order  to  secure  a  fair  representation 
of  the  supply  and  to  avoid  introduction  of  foreign 
matters.  The  five-pint  green  glass-stoppered 
bottles  used  for  holding  acids  are  suitable  for 
containing  the  samples.  The  contents  of  one 
such  bottle  will  suffice  for  most  sanitary  or  technic 
examinations.  Several  forms  of  boxed  bottles 
are  now  manufactured.  Most  of  these  are  pro- 
vided with  a  hinged  lid  that  can  be  fastened  by  a 
padlock  which  is  sometimes  advisable.  The 
green  glass-stoppered  bottles  may  be  fitted  in 
such  an  arrangement.  Crated  demijohns  are 
now  made  for  forwarding  water.  The  larger 
sizes  are  well  adapted  for  samples  which  are  to  be 
subjected  to  elaborate  analysis.  A  boxed  bottle 
called  the  "New  Era  demijohn"  is  also  suitable. 
Stone  jugs,  casks,  or  metal  vessels  should  not  be 
employed.  The  bottles  used  must  be  thoroughly 
rinsed  several  times  with  the  water  to  be  ex- 
amined, filled,  and  the  stopper  tied  down  or 

8 


PRELIMINARY   EXAMINATION.  9 

fastened  by  stretching  a  rubber  finger-cot  over 
the  stopper  and  lip.  If  corks  are  used,  they 
should  be  new  and  thoroughly  rinsed.  Wax, 
putty,  plaster,  or  similar  material  should  not  be 
used. 

In  taking  samples  from  lakes,  slow  streams,  or 
reservoirs,  it  is  necessary  to  submerge  the  bottle 
so  as  to  avoid  collecting  any  water  that  has  been 
in  immediate  contact  with  the  air.  In  the  ex- 
amination of  public  water-supplies,  the  sample 
should  be  drawn  from  a  hydrant  in  direct  con- 
nection with  the  main,  and  not  from  a  cistern, 
storage-tank,  or  dead  end  of  a  pipe.  In  the  case 
of  pump-wells,  a  few  gallons  of  water  should  be 
pumped  out  before  taking  the  sample,  in  order  to 
remove  that  which  has  been  standing  in  the  pipe. 

In  all  cases  care  should  be  taken  to  fill  the  vessel 
with  as  little  agitation -with  air  as  possible. 

It  is  important  that  with  each  sample  a  record 
be  made  of  those  surroundings  and  conditions 
which  might  influence  the  character  of  the  water, 
particularly  in  reference  to  sources  of  pollution, 
such  as  proximity  to  cesspools,  sewers,  or  manu- 
facturing establishments.  The  character  and 
condition  of  the  different  strata  of  the  locality 
should  be  noted  if  possible. 

Determinations  of  nitrogen  existing  as  am- 
monium compounds  and  as  organic  matter,  and 
of  oxygen-consuming  power,  should  be  made 


IO 


ANALYTIC    OPERATIONS. 


upon  the  sample  in  the  original  condition,  whether 
turbid  or  clear,  but  all  other  estimations  should 
be  made  upon  the  clear  liquid. 
Turbid  waters  may  be  clarified  by 
standing  or  by  filtration;  for  the 
latter  purpose  Schleicher  &  SchuH's 
extra  heavy  No.  598  paper  is  the 
best.  In  many  cases  the  suspended 
matter  can  not  be  entirely  re- 
moved by  filtration,  and  subsidence 
must  be  resorted  to.  The  use  of  a 
small  quantity  of  alum,  or  alumi- 
num hydroxid,  as  described  in  the 
section  on  the  purification  of  water, 
will  sometimes  be  applicable  as  a 
means  of  clarifying  samples.  For 
the  quantitative  determination, 
the  sediment  from  a  known  volume 
of  the  water  is  collected  on  a  tared 
filter,  dried,  and  weighed. 

The  water  from  newly  dug  wells 
is  generally  turbid,  and  the  deter- 
minations are  best  made  after  fil- 
tration; but  the  results  will  be  un- 
satisfactory, showing  a  higher  pro- 
FIG.  i.          portion  of  organic  matter  than  will 
be  found  when  the  supply  becomes  clear. 

Collection  of  Samples  for  Bacteriologic  Exami- 
nation.— Bacteriologic  examinations  are  of  little 


PRELIMINARY    EXAMINATION.  II 

value  unless  made  promptly  on  samples  that 
have  been  collected  with  precautions  against 
contamination.  The  inoculation  of  the  culture- 
medium  is  best  done  at  the  source.  If  this  is  not 
possible,  glass-stoppered  bottles  holding  about 
200  c.c.,  which  have  been  thoroughly  sterilized, 
with  stoppers  in  place,  in  a  hot-air  oven  at  100°, 
must  be  used  for  collection.  They  should 
be  rinsed  on  the  outside  with  the  water,  dipped 
below  the  surface,  the  stopper  withdrawn,  and 
again  inserted  when  the  bottle  is  full.  If  these 
are  to  be  transported  any  distance,  they  should  be 
packed  in  ice.  For  the  collection  of  samples 
below  the  surface  of  the  water,  the  bottle  shown 
in  the  cut  (Fig.  i)  is  recommended  by  Abbott. 
The  bottle  having  been  previously  thoroughly 
sterilized  is  sunk  to  the  proper  depth  and  the 
stopper  is  then  lifted  by  a  special  cord  and  held 
until  the  bottle  is  full,  when,  the  cord  being  re- 
leased, the  stopper  falls.  Before  taking  out 
portions  for  test,  the  lip  and  stopper  must  be 
thoroughly  sterilized  by  strong  alcohol  and  by 
careful  heating,  and,  after  cooling,  washing  with 
sterilized  water. 

This  bottle  can  also  be  used  for  taking  samples 
for  chemical  analysis  except  determination  of 
dissolved  gases. 

Color. — "Apparent"  color  is  that  of  the  water 
in  its  raw  state,  "true"  color  that  of  the  water 


12  ANALYTIC    OPERATIONS. 

free  from  suspended  matter.  Unless  otherwise 
stated,  true  color  is  meant.  The  APHA  gives 
preference  to  Hazen's  method,  as  follows: 

1.246  grams  of  potassium  platinic  chlorid 
(0.5  gram  of  Pt)  and  i  gram  of  crystallized 
cobalt  chlorid  (0.25  gram  of  Co)  are  dissolved  in 
water,  100  c.c.  of  strong  hydrochloric  acid  added, 
and  the  solution  made  up  to  1000  c.c.  It  keeps 
well,  even  when  exposed  to  the  light.  For  com- 
parison, i,  2,  3,  etc.,  of  the  stock  solution  are 
diluted  to  50  c.c.  in  Nessler  tubes.  These  corre- 
spond to  o.i,  0.2,  0.3,  etc.,  degrees  of  the  color 
standard.  These  also  keep  for  a  long  time  if 
protected  from  dust. 

Determinations  should,  of  course,  be  made  only 
on  clear  samples.  The  results  are  expressed  in 
whole  numbers,  thus: 

Color  between      i  and    50  to  nearest  unit 
Color  between    51  and  100  to  nearest    5 
Color  between  101  and  250  to  nearest  10 
Color  between  251  and  500  to  nearest  20 

Waters  registering  above  70  should  be  diluted  and 
re-examined. 

Odor. — This  is  to  be  observed  at  ordinary  tem- 
peratures (cold  odor)  and  near  the  boiling  point 
(hot  odor). 

Cold  odor  is  best  observed  by  shaking  a  moder- 
ate amount  of  the  sample  for  a  few  moments  in  a 


PRELIMINARY    EXAMINATION.  13 

stoppered  bottle,  about  half  filled,  removing 
the  stopper  and  noting  the  odor  promptly.  Hot 
odor  is  detected  as  follows:  About  300  c.c.  are  put 
into  an  Erlenmyer  flask,  the  mouth  covered  with 
a  watch-glass  and  the  liquid  heated  to  just  below 
the  boiling  point,  allowed  to  cool  for  five  minutes 
and  the  odor  noted. 

The  results  of  odor  tests  are  often  valuable  as 
suggestions  of  certain  kinds  of  contamination, 
but  the  data  must  be  used  with  care,  and  espe- 
cially the  analyst  must  not  forget  that  odors  may 
be  due  to  unclean  bottles,  and  very  frequently  to 
unclean  corks.  A  common  incident  of  the  com- 
mercial laboratory  is  to  get  a  water  sample  with 
an  odor  due  to  the  use  of  a  cork  from  a  wine  or 
whisky  bottle  or  vinegar  jug. 

Turbidity. — The  standard  now  in  use  is  that 
adapted  by  the  U.  S.  Geologic  Survey,  which  is 
that  a  turbidity  of  100  is  that  exhibited  by  a 
water  containing  in  suspension  100  parts  per 
million  of  a  standard  material  in  such  a  state 
of  fineness  that  a  bright  platinum  wire  i  mm. 
in  diameter  can  just  be  seen  when  the  center  of 
the  wire  is  1.2  meters  below  the  surface  of  the 
water,  the  observation  being  made  in  the  open  air 
in  daylight,  but  not  in  sunlight  and  in  a  vessel 
so  large  that  the  sides  do  not  affect  the  result. 

The  material  is  elutriated  fuller's  earth,  dried, 
and  passed  through  a  2oo-mesh  sieve,  i  gram  of 


14  ANALYTIC    OPERATIONS. 

this  in  1000  c.c.  of  distilled  water  makes  a  stock 
suspension,  which  should  have  a  turbidity  of 
1000.  This  suspension  must  be  tested  by  dilu- 
ting a  portion  of  it  by  nine  volumes  of  clear  water 
and  determining  if  the  material  has  the  proper 
degree  of  fineness  to  register  100.  If  not,  it  must 
be  corrected  by  the  addition  of  water  or  of 
material  as  the  case  may  be.  From  the  stock 
solution  standards  are  prepared  by  dilution  with 
distilled  water.  For  readings  below  20  it  is  rec- 
ommended that  the  standards  be  kept  in  bottles 
similar  to  those  used  in  collecting  samples.  For 
readings  from  20  to  100  in  100  c.c.  Nessler  tubes, 
about  20  mm.  in  diameter.  Standards  must 
be  kept  stoppered  and  be  thoroughly  shaken  be- 
fore making  comparisons.  To  prevent  vegetable 
growths,  a  small  amount  of  mercuric  chlorid  may 
be  added  to  each. 

The  standard  apparatus  for  this  method  is 
known  as  U.  S.  G.  S.  turbidity  rod  of  1902.  On  a 
glass  rod,  about  1.5  meters  long,  is  fixed  at  25  mm. 
from  one  end  and  at  a  right  angle,  a  platinum 
wire  25  mm.  long  and  i  mm.  in  diameter.  At  a 
distance  of  1.2  meters  from  the  center  of  the  cross- 
section  of  this  wire  is  fixed  a  wire  ring  so  that  the 
opening  is  just  above  the  wire.  The  point  100 
mm.  above  the  center  of  the  wire  is  marked  as  100, 
and  the  other  proportions  are  marked  as  deter- 
mined empirically  by  the  U.  S.  G.  S.,  according 


PRELIMINARY   EXAMINATION.  15 

to  the  annexed  table,  which  gives  only  some  of 
the  points.  T  is  the  degree  of  turbidity  obtained 
from  standards  made  as  indicated  above;  V  the 
distance  in  mm.  above  the  wire  at  which  the 
surface  of  the  water  touches  the  rod,  when  the 
wire  is  just  at  the  limit  of  visibility.  Samples 
that  have  a  turbidity  above  500  should  be  diluted 
and  re-examined,  allowance  being  made  for  such 
dilution. 


7  1095  150  72.0 
10  794  200  57.4 
15  S5i  250  49.1 

20  426  300  43.2 

30      296      400      35.4 

40  228  500  30.9 

50  187  600  27.7 

60  158  1000  20.9 

70  138  1500  17.1 

80  122  2000  14.8 

90  1 10  300O  12. I 

IOO  IOO 

Reaction. — Most  natural  waters  are  alkaline 
to  the  common  indicators,  but  titration  often 
gives  a  clue  to  the  proportion  of  carbonates  pres- 
ent. Mine  waters  are  often  acid,  also  some  deep 
waters,  and  occasionally  surface  waters  drawn 
from  areas  rich  in  vegetable  matters.  Measure- 
ments of  alkalinity  are  made  regularly  in  con- 
nection with  the  determination  of  the  several 
forms  of  hardness ;  the  standard  methods  for  such 
purposes  are  described  under  that  head.  It  is 
of  some  interest  to  keep  a  record  of  alkalinity  of 


1 6  ANALYTIC    OPERATIONS. 

samples  in  routine  laboratory  work,  which  is 
easily  done  by  titrating  250  c.c.  with  standard 
acid  using  the  same  indicator  for  all  tests  that 
are  to  be  compared. 

ACIDITY. — The  most  frequent  causes  of  acidity 
in  natural  waters  are,  carbonic  acid,  iron  and 
aluminum  sulfates  and  sulfuric  acid,  any  or  all 
of  which  may  be  present.  Distinction  may  be 
made  by  titrating  with  standard  sodium  carbon- 
ate, using  different  indicators  under  special 
conditions. 

Phenolphthalein  at  room  temperature  gives  the 
total  acidity  due  to  all  the  above  substances. 
At  100°  it  gives  all  except  that  for  carbonic  acid. 

Methyl  orange  in  the  cold  gives  the  acidity  due 
to  sulfuric  acid. 

It  will  be  seen  that  by  these  methods  the  car- 
bonic and  sulfuric  acidity  can  be  ascertained, 
and,  if  the  iron  is  determined  by  one  of  the 
standard  methods,  that  due  to  aluminum  sulfate 
can  be  calculated. 

TOTAL  SOLIDS. 

A  platinum  basin  holding  100  c.c.  will  be  found 
convenient  for  this  determination.  This  will 
weigh  about  45  grams.  It  should  be  kept  clean 
and  smooth  by  frequent  burnishing  with  sand,  a 
little  of  which  should  be  placed  in  the  palm  of  the 
hand,  moistened,  and  the  dish  gently  rubbed 


TOTAL   SOLIDS.  17 

against  it.  Very  fine  sea-sand  with  round, 
smooth  grains  is  the  only  kind  suitable  for  this 
purpose.  Coarse  river  sand,  tripoli,  or  other 
rough  scouring-powders  must  not  be  employed. 
If  proper  care  is  taken,  the  luster  of  the  metal  will 
be  retained,  and  the  loss  in  weight  will  be  trifling. 
The  inner  surface  can  generally  be  cleaned  by 
treatment  with  hydrochloric  acid,  rinsing,  and, 
if  necessary,  burnishing 
with  sand.  Neglect  of 
these  precautions  will  soon 
lead  to  serious  damage  to 
the  dish.  A  small,  smooth 
slab  of  iron  or  marble  is 
convenient  to  set-  it  on 
while  cooling.  When  being 
heated  over  the  naked  ,PIG  a 

flame,  the  dish  should  rest 

on  a  triangle  of  iron  wire,  covered  with  pipe- 
stems.  Dishes  of  pure  nickel  are  not  satisfactory 
substitutes  for  those  of  platinum. 

Platinum-pointed  forceps  should  be  used  in 
handling  the  dish.  The  platinum  terminals  may 
be  kept  bright  and  clean  by  the  use  of  sand. 

The  low-temperature  burner,  used  as  shown  in 
Fig.  2,  will  be  found  a  very  convenient  substi- 
tute for  the  water-bath  and  hot-air  oven.  The 
inlet  pipe  is  very  short  and  soon  becomes  so  hot  as 
to  injure  the  rubber  tube.  To  avoid  this  it  may 


1 8  ANALYTIC    OPERATIONS. 

be  lengthened  by  means  of  a  piece  of  J-inch  gas- 
pipe,  or  the  junction  may  be  wrapped  with  a  rag, 
the  ends  of  which  dip  into  water.  By  capillary 
attraction  the  rag  is  kept  moist  and  cool. 

The  determination  of  total  solids  is  made  by 
evaporating  100  c.c.  of  the  water  in  the  platinum 
basin,  which  has  been  previously  heated  almost 
to  redness,  allowed  to  cool  for  ten  minutes,  and 
weighed.  The  operation  is  conducted  at  a  mod- 
erate heat.  When  the  residue  appears  dry,  the 
heat  may  be  increased  slightly  for  some  minutes. 
The  above  method  will  answer  in  most  cases.  In 
waters  of  exceptional  purity  it  may  be  advisable 
to  use  larger  quantities,  such  as  250  c.c.  When 
the  residue  contains  deliquescent  bodies,  the  de- 
termination will  not  be  accurate,  and  when  ap- 
preciable amounts  of  magnesium  and  chlorin  are 
present,  a  decomposition  will  occur  toward  the 
close  of  the  evaporation  by  which  magnesium  oxid 
will  be  formed  and  hydrogen  chlorid  escape. 

The  irregular  decomposition  occurring  during 
the  evaporation  may  be  largely  prevented  by  add- 
ing 0.005  gram  of  sodium  carbonate  to  each  100 
c.c.  of  the  sample  taken.  This  converts  magne- 
sium and  calcium  salts  into  carbonates.  The 
sodium  carbonate  is  conveniently  kept  in  the 
form  of  solution  of  such  strength  that  i  c.c.  con- 
tains o.oo i  gram.  The  weight  of  the  carbonate  is, 
of  course,  to  be  deducted  from  the  weight  of  the 


TOTAL   SOLIDS.  19 

residue.  Drown  and  Hazen  have  carefully  in- 
vestigated this  method  and  have  found  it  avail- 
able for  a  more  satisfactory  determination  of  the 
loss  on  ignition.  For  this  process  they  place  the 
platinum  basin  containing  the  residue  within 
another  similar  basin  of  such  size  that  an  air- 
space of  about  one-half  of  an  inch  is  left  all 
around  the  inner  dish,  which  is  supported  upon  a 
spiral  of  platinum  that  rests  on  the  bottom  of  the 
outer  dish.  Over  the  inner  dish  is  suspended  a 
disc  of  platinum  foil  to  reflect  the  heat.  The 
outer  dish  is  heated  to  bright  redness. 

After  the  weight  of  the  residue  is  obtained,  the 
dish  should  be  cautiously  heated  to  low  redness 
and  the  effect  noted.  Nitrates  and  nitrites, 
calcium  and  magnesium  carbonates,  are  decom- 
posed; ammonium  salts  are  driven  off;  potassium 
and  sodium  chlorids  are  also  driven  off  if  the 
temperature  is  high.  Organic  matter  is  at  first 
charred,  and  by  continued  heating  burned  off. 
When  the  quantity  of  nitrates  is  considerable, 
slight  deflagration  may  be  observed,  or  the  pro- 
duction of  red  fumes  of  nitrogen  dioxid.  The 
organic  matter,  in  decomposing,  not  infrequently 
develops  odors  which  indicate  its  character  or 
source.  These  are  more  satisfactorily  observed 
when  a  rather  large  quantity,  say  250  c.c.,  is 
evaporated  at  a  low  heat,  preferably  on  a  water- 
bath. 


20  ANALYTIC    OPERATIONS. 

In  water  of  high  organic  purity,  the  residue  on 
heating  will  give  no  appreciable  blackening  nor 
odor,  while  in  forest  streams  charged  with  vege- 
table matter  derived  from  falling  leaves,  very  de- 
cided blackening  without  unpleasant  odor  will 
be  noticed.  The  loss  of  weight  after  heating 
can  not  be  taken  as  a  measure  of  the  organic 
matter,  except  when  present  in  relatively  large 
amount. 

Increase  in  the  price  of  platinum  has  led  to 
the  use  of  glass  and  porcelain  dishes.  The  quartz 
dishes  now  available  are  also  suitable.  Dishes 
made  of  such  materials  must  be  carefully  cleaned, 
warmed,  cooled  (in  the  desiccator)  before  each 
determination.  For  the  accurate  determination 
of  the  mineral  ingredients,  evaporation  in  plat- 
inum is  indispensable. 

CHLORIN. 

Reagents : 

Standard  Silver  Nitrate. — Dissolve  about  5 
grams  of  pure  recrystallized  silver  -nitrate  in  dis- 
tilled water,  and  make  the  solution  up  to  1000  c.c. 
The  amount  of  chlorin  to  which  this  is  equivalent 
may  be  determined  as  follows:  Several  grams 
of  pure  sodium  chlorid  are  finely  powdered  and 
heated  over  a  Bunsen  burner  for  five  minutes,  not 
quite  to  redness.  When  cold,  0.824  gram  are  dis- 
solved in  water  and  the  solution  made  up  to  500 


CHLORIN.  21 

c.c.  25  c.c.  of  this  should  be  diluted  to  250  c.c. 
with  distilled  water  and  tested  as  described  below, 
and  the  amount  of  silver  solution  required  noted. 
Each  c.c.  of  the  sodium  chlorid  solution  contains 
o.oo i  gram  chlorin. 

Potassium  Chromate. — 5  grams  of  potassium 
chromate  are  dissolved  in  100  c.c.  of  distilled 
water.  A  solution  of  silver  nitrate  is  added  until 
a  permanent  red  precipitate  is  produced,  which  is 
separated  by  filtration. 

Aluminum  Hydroxid — (For  decolorization)  25 
grams  of  ammonium  (or  potassium)  alum  are 
dissolved  in  200  c.c.  of  water,  ammonium  hy- 
droxid  carefully  added  to  slight  excess,  the  pre- 
cipitate washed  until  free  from  chlorids  and 
ammonium  compounds  and  kept  in  a  closed 
bottle. 
Process : 

If  a  preliminary  test  shows  the  chlorin  to  be 
present  in  considerable  amount,  the  determina- 
tion may  be  made  on  100  c.c.  of  the  water  without 
concentration.  If,  however,  there  is  but  little 
present,  250  c.c.  should  be  evaporated  to  about 
one-fifth,  with  the  addition  of  sodium  carbonate, 
and  the  determination  made  on  the  concentrated 
liquid  after  cooling. 

The  water  is  placed  in  a  porcelain  dish  or  in  a 
beaker  standing  on  a  white  surface,  a  few  drops 
of  potassium  chromate  solution  added,  and  stand- 


22  ANALYTIC    OPERATIONS. 

ard  silver  nitrate  solution  run  in  from  a  buret 
until  a  faint  red  color  of  silver  chromate  remains 
permanent  on  stirring.  The  proportion  of  chlorin 
is  then  calculated  from  the  number  of  c.c.  of 
silver  solution  added.  Greater  accuracy  is  se- 
cured by  operating  in  yellow  light.  A  second 
determination  may  be  made,  using  as  a  compari- 
son the  liquid  first  titrated,  the  red  color  having 
been  previously  discharged  by  a  few  drops  of 
sodium  chlorid  solution. 

The  water  should  always  be  as  nearly  neutral 
as  possible  before  titration.  If  acid,  it  may  be 
neutralized  by  the  addition  of  sodium  carbonate. 
If  alkaline  hydroxids  are  present,  dilute  sulfuric 
acid  should  be  added  until  the  liquid  will  just 
discharge  the  color  of  phenolphthalein.  If  the 
sample  has  a  distinct  color  not  removable  by 
simple  filtration,  a  volume  of  aluminum  hydroxid 
(about  3  c.c.)  should  be  added  to  500  c.c.,  the 
mixture  heated  to  boiling,  cooled,  filtered  and 
titrated. 

NITROGEN  IN  AMMONIUM  COMPOUNDS 
("FREE  AMMONIA")  AND  IN  ORGANIC 
MATTER  ("ALBUMINOID  AMMONIA"). 

Most  natural  waters  contain  ammonium  com- 
pounds, the  exact  form  being  often  uncertain, 
but  at  the  boiling  point  the  carbonates  form  am- 


NITROGEN    IN    AMMONIUM    COMPOUNDS.        23 

monium  carbonate,  which  dissociates  and  dis- 
tils. From  such  waters,  therefore,  the  whole  of 
the  ammonium  compounds  can  be  removed  by 
distillation.  If  carbonates  are  deficient,  a  small 
pro-amount  of  sodium  carbonate  must  be  added. 
The  nitrogen  in  the  organic  matter  can  be  partly 
converted  into  ammonium  hydroxid  by  boiling 
with  a  strongly  alkaline  solution  of  potassium 
permanganate  (alkaline  permanganate)  and  this 
ammonium  hydroxid  can  also  be  collected  by 
distillation. 

Procedures  based  on  this  principle,  due  to 
Wanklyn,  are  extensively  used  by  American  and 
English  chemists.  The  inappropriate  terms,  in- 
troduced by  Wanklyn,  based  on  erroneous  in- 
ferences are  still  used ;  the  ammonium  compounds 
existing  in  the  water  being  called  "free  ammonia" 
— which  they  never  are — and  the  ammonium 
hydroxid  obtained  from  the  organic  matter  being 
called  "albuminoid  ammonia" — which  it  rarely 
is.  It  is  much  better  to  state  the  data,  respect- 
ively as  "nitrogen  as  ammonium"  and  "nitrogen 
by  permanganate. " 

Except  in  waters  rich  in  ammonium  compounds, 
such  as  sewage  and  sewage-disposal  effluents,  in 
which  the  ammonium  may  sometimes  be  deter- 
mined directly,  the  procedures  are  by  distillation 
and  the  data  obtained  by  color  comparisons  with 
standards  of  known  composition. 


24  ANALYTIC   OPERATIONS. 

Apparatus : 

Distilling  Apparatus. — Many  forms  have  been 
devised;  Fig.  3  is  satisfactory.  The  flask  should 
be  Jena,  or  similar  glass;  the  condenser  is  a  form 
devised  by  Cribb,  but  modified  by  Hopkins,  by 
whose  name  it  is  generally  known.  Many 


FIG.  3. 

chemists  prefer  block- tin  tubes  for  condensing. 
The  Kjeldahl  apparatus  in  use  in  the  laboratory 
should  not  be  employed  for  this  work.  A  stout 
piece  of  asbestos  should  be  placed  between  the 
flask  and  condenser,  as  shown,  to  avoid  radiation 
of  heat. 


NITROGEN   IN    AMMONIUM    COMPOUNDS.        25 

Nessler  Glasses. — Narrow  cylinders  of  colorless 
glass  about  15  mm.  in  diameter  polished  on  the 
outside  of  the  base.  Dealers  now  furnish  stand- 
ard forms.  In  selecting  a  set,  tubes  as  nearly 
uniform  as  possible  should  be  chosen. 
Reagents : 

Ammonium-free  Water. — If  the  distilled  water 
of  the  laboratory  gives  a  reaction  with  Nessler 
reagent,  it  should  be  treated  with  sodium  car- 
bonate, about  i  grain  to  the  liter,  and  boiled 
until  about  one-fourth  has  been  evaporated. 
Ammonium-free  water  may  be  obtained  by  dis- 
tilling, in  a  retort,  ordinary  water  made  slightly 
acid  with  sulfuric  acid. 

Messrs.  J.  B.  Weems,  C.  E.  Gray,  and  E.  C. 
Myers  recommend  the  following  method:  Sod- 
ium dioxid  is  added  to  ordinary  water  in  the  pro- 
portion of  i  gram  to  1000  c.c.  and  the  liquid 
boiled  for  thirty  minutes,  or  longer  if  the  amount 
of  ammonium  compounds  is  high.  It  is  then 
cooled  and  the  flask  kept  closed.  Flasks  holding 
several  i  ooo  c.c.  are  most  convenient.  If  the  water 
is  distilled,  the  distillate  may  also  be  used  for 
the  preparation  of  standard  nitrate  and  nitrite 
solutions. 

Standard  Ammonium  Chlorid. — Dissolve  0.382 
gram  of  pure  dry  ammonium  chlorid  in  100  c.c.  of 
ammoniurn-free  water.  For  use,  dilute  i  c.c. 
of  this  solution  with  pure  water  to  100  c.c.  i  c.c. 


26  ANALYTIC    OPERATIONS. 

of  this  dilute  solution  contains  o.ooooi  gram  of 
nitrogen. 

Nessler's  Reagent. — (APHA  formula).  Dissolve 
50  grams  of  potassium  iodid  in  a  minimum  quan- 
tity of  water;  add  saturated  solution  of  mercuric 
chlorid  in  small  portions  with  constant  stirring 
until  a  slight  precipitate  persists;  add  400  c.c. 
of  a  clear  50  per  cent,  solution  of  potassium 
hydroxid,  stir,  dilute  to  1000  c.c.,  allow 
to  settle  and  decant.  The  solution  should 
give  the  full  color  reaction  within  five 
minutes,  and  should  not  give  a  precipitate 
in  two  hours  with  small  amounts  of  am- 
JT-  monium  compounds.  Nessler  and  similar 

U, reagents  should  be  kept  in  capped  bottles 

FlG  4    as  shown  in  Fig.  4   in  which  the  pipet 

may  remain  when  not  in  use. 
Alkaline  Permanganate. — 8  grams  of  potassium 
permanganate  and  200  grams  of  potassium  hy- 
droxid of  good  quality  are  dissolved  in  1000  c.c.  of 
distilled  water.  It  is  customary  to  boil  this 
liquid  to  purify  it  from  ammonium  compounds 
and  organic  matter  producing  ammonia,  and  it 
is  also  recommended  to  make  blank  experiments 
with  the  portions  taken  for  use,  but  the  procedure 
of  twin  distillation,  herewith  described  renders 
these  manipulations  unnecessary. 

Pumice. — Fragments  of  pumice  are  kept  in  a 
wide-mouth  stoppered  bottle  with  water.     They 


NITROGEN    IN    AMMONIUM    COMPOUNDS.        27 

soon  become  water-logged.  If  it  is  desired  to  pre- 
pare pumice  for  immediate  use,  fragments  should 
be  heated  to  near  redness  and  plunged  into  water. 
Process: 

The  distillation  apparatus  is  set  up  in  pairs; 
each  flask  is  rinsed  and  charged  with  200  c.c.  of 
pure  water.  To  one  is  added  a  pinch  of  sodium 
carbonate:  to  the  other  50  c.c.  of  the  alkaline 
permanganate.  A  few  fragments  of  pumice  are 
put  in  each  to  prevent  bumping.  The  liquids  are 
distilled  at  such  a  rate  that  50  c.c.  pass  over  from 
each  flask  in  about  ten  minutes,  and  the  distill- 
ates tested  for  ammonium  compounds,  as  noted 
below,  and  when  no  more  is  coming  off,  which  will 
generally  be  when  the  volume  is  reduced  to  100 
c.c.,  25oc.c.  of  the  sample  are  added  to  each  flask 
and  the  distillation  resumed.  Long-stemmed  fun- 
nels are  convenient  for  introducing  liquids.  The 
distillates  are  collected  in  Nessler  tubes  in  quan- 
tities of  50  c.c.  each  and  tested  as  described  below. 

The  flask  containing  sodium  carbonate  fur- 
nishes only  the  ammonium  existing  in  the  sample 
(so-called  "free  ammonia");  the  flask  containing 
the  alkaline  permanganate  furnishes  also  the  pre- 
existing ammonium  and,  in  addition,  the  ammo- 
nium formed  from  the  organic  matter.  There- 
fore, the  figure  obtained  from  distillates  from  the 
sodium  carbonate  should  be  deducted  from  that 
obtained  from  the  other  flask;  the  remainder  will 


28  ANALYTIC    OPERATIONS. 

be  the  ammonium  formed  from  the  organic  mat- 
ter (so-called  "albuminoid  ammonia"). 

The  determination  of  the  amounts  of  ammo- 
nium compounds  in  the  distillates  is  called  "ness- 
lerizing"  and  is  conducted  as  follows: 

Standards  are  prepared  by  charging  Nessler  tubes 
with  the  following  amounts  of  the  dilute  ammo- 
nium chlorid  solution  (see  page  25)  o.i  c.c.,  0.2  c.c., 
0.5  c.c.,  i.o  c.c.,  1.5  c.c.,  2.0  c.c.,  and  so  on  accord- 
ing to  the  probable  amount  to  be  measured, 
not  going  above  6.0  c.c.  Each  tube  is  then  filled 
to  the  50  c.c.  mark  with  water  free  from  ammo- 
nium compounds.  The  standard  tubes  and  those 
containing  the  distillates  are  placed  so  that  they 
can  be  compared  by  looking  vertically  through 
the  liquids  and  2  c.c.  of  Nessler  reagent  added  to 
each  running  this  in  at  the  top  of  the  liquid  and 
allowing  it  to  diffuse  by  gravity.  At  the  end  of 
ten  minutes  the  colors  in  the  distillates  should 
be  compared  with  those  of  the  standard  tubes. 
Equality  in  depth  of  color  indicates  equality  of 
ammonium  content.  Each  c.c.  of  the  dilute 
ammonium  chlorid  solution  contains  o.ooooi  of 
nitrogen.  Standards  and  distillates  must  be 
compared  at  the  same  temperature.  Many  anal- 
ysts keep  each  50  c.c.  of  distillate  separate  for 
test.  With  waters  containing  but  little  ammo- 
nium compounds  or  organic  matter,  the  distillates 
from  a  given  flask  may  be  mixed,  made  up  to  defi- 


TOTAL   ORGANIC    NITROGEN.  29 

nite  volume  with  pure  water,  an  aliquot  part 
tested  and  calculation  made. 

The  comparison  standards  must  be  made  up 
each  day  as  they  do  not  keep.  If  the  color  in  any 
distillate  is  very  deep,  the  liquid  may  be  diluted 
considerably  with  a  known  volume  of  pure  water, 
50  c.c.  of  this  compared  and  calculation  made. 
When  the  amount  of  ammonium  hydroxid  in  the 
distillate  is  considerable  a  precipitate  may  occur. 
Such  a  result  is  useless  and  a  new  distillation  must 
be  made  using  either  less  of  the  sample  or  dilut- 
ing the  distillate  considerably  with  pure  water. 

As  small  quantities  of  ammonium  compounds 
and  nitrogenous  matters  are  everywhere  present, 
the  greatest  care  should  be  exercised  in  order  to 
avoid  their  introduction  in  any  way  during  the 
course  of  the  analysis.  All  measuring  vessels, 
cylinders,  etc.,  should  be  thoroughly  rinsed  before 
using. 

TOTAL  ORGANIC  NITROGEN 

Several  processes  for  the  determination  of  the 
organic  nitrogen  in  water,  based  on  those  in  use 
in  ordinary  organic  analysis,  have  been  devised. 

The  ease  and  certainty  with  which  the  nitrogen 
of  most  organic  bodies  may  be  converted  into 
ammonium  sulfate  by  boiling  with  sulfuric  acid, 
offers  a  means  of  determination  free  from  the  ob- 
jections of  former  methods.  The  method  intro- 


30  ANALYTIC    OPERATIONS. 

duced  by  Kjeldahl  for  general  organic  analysis  was 
first  successfully  applied  to  water  analysis  by 
Drown  and  Martin. 

In  their  original  process,  500  c.c.  was  concen- 
trated to  about  300  c.c.,  and  the  distillate  nessler- 
ized  for  determining  the  nitrogen  existing  as 
ammonium  compounds.  The  organic  nitrogen 
was  then  determined  in  the  residual  water.  Ow- 
ing to  the  fact  that  organic  matter  may  be 
decomposed  by  moderate  heat,  there  is  liability 
to  underestimation  of  the  nitrogen.  The  follow- 
ing procedure  suggested  by  Leffmann  and  Beam, 
eliminates  that  loss  and  enables  determinations 
to  be  made  without  distillation. 
Reagents : 

Concentrated  Sulfuric  Acid. — This  should  not 
contain  appreciable  quantities  of  nitrogen.  It 
can  now  be  obtained  of  high  purity. 

Sodium  Hydroxid  Solution. — The  white  granu- 
lated material  sold  for  domestic  uses  (concen- 
trated lye)  will  answer  100;  grams  are  dissolved 
in  about  1000  c.c.  of  water,  the  liquid  boiled  down 
to  one-half  volume  and  diluted  to  1000  c.c.  by 
addition  of  water  that  gives  no  color  with  Nessler 
reagent. 

Sodium  Carbonate  Solution. — 200  grams  of  good 
sodium  carbonate  are  dissolved  in  about  1000  c.c. 
of  water  and  the  solution  boiled  briskly  until 
several  hundred  c.c.  are  driven  off. 


TOTAL   ORGANIC    NITROGEN.  31 

All  reagents   must  be  kept  in  well-stoppered 
bottles,  protected  from  dust  and  fumes  of  am- 
monium compounds. 
Process : 

Nitrogen  as  Ammonium. — 200  c.c.  of  the  water 
are  placed  in  a  stoppered  bottle,  2  c.c.  each  of  the 
solutions  of  sodium  carbonate  and  sodium  hy- 
droxid  added,  the  stopper  inserted,  the  solutions 
mixed  and  allowed  to  stand  for  an  hour  or  two.  A 
filter  is  prepared  by  inserting  a  rather  large  plug 
of  absorbent  cotton  in  a  funnel.  This  should 
be  washed  with  ammonium-free  water  until  the 
filtrate  gives  no  color  with  Nessler  reagent. 
The  clear  portion  of  the  sample  is  drawn  off  with 
a  pipet  and  run  through  the  filter,  the  first  por- 
tions being  rejected,  since  it  is  diluted  by  the  water 
retained  in  the  cotton.  The  filtration  is  rapid; 
when  sufficient  filtrate  is  collected,  an  aliquot 
part  is  nesslerized  and  the  calculation  for  the 
whole  volume  made. 

Total  Organic  and  Ammoniacal  Nitrogen. — 500 
c.c.  of  the  sample  are  mixed  with  10  c.c.  of  the 
sulfuric  acid,  boiled  until  the  water  is  all  evapo- 
rated, and  the  remaining  liquid  colorless  or  pale 
yellow,  a  small  amount  of  potassium  permangan- 
ate added  and  the  liquid  again  boiled  until  color- 
less, which  will  require  but  little  time.  If  the 
permanganate  produces  a  purple  solution  at 
first,  the  original  heating  was  not  sufficient,  and 


32  ANALYTIC    OPERATIONS. 

the  mass  should  be  heated  for  some  extra  time 
after  the  color  produced  by  the  permanganate  is 
discharged.  After  completion  of  the  heating  the 
liquid  is  cooled  to  room  temperature,  50  c.c.  of 
ammonium-free  water  added,  then  sufficient  of 
the  sodium  hydroxid  solution  to  render  the  liquid 
slightly  alkaline — about  150  c.c.  will  be  usually 
required — and  2  c.c.  of  sodium  carbonate  solu- 
tion to  precipitate  the  calcium  and  magnesium. 
The  mixture  is  cooled  by  immersion  of  the  flask 
in  water,  made  up  to  250  c.c.,  transferred  to  a 
stoppered  bottle,  allowed  to  settle — about  an 
hour  will  be  usually  required — sufficient  of  the 
clear  liquid  filtered  as  in  the  ammonium  deter- 
mination, and  an  aliquot  part  nesslerized. 

Of  course,  the  ammonium  obtained  in  the  first 
process  is  deducted  from  that  obtained  in  the 
second,  making  due  allowance  for  the  different 
proportions  of  the  sample  used  in  the  two  cases; 
the  remainder  is  the  nitrogen  existing  in  organic 
matter. 

Blank  experiments  should  be  made  to  deter- 
mine the  purity  of  the  reagents. 

NITROGEN  AS  NITRATES. 

Reagents : 

Standard  Potassium  Nitrate. — 0.722  gram  of 
potassium  nitrate,  previously  heated  to  a  tern- 


NITROGEN   AS    NITRATES.  33 

perature  just  sufficient  to  fuse  it,  are  dissolved 
in  water,  and  the  solution  made  up  to  1000  c.c. 
i  c.c.  of  this  solution  will  contain  o.oooi  gram 
of  nitrogen. 

Phenoldisulfonic  Acid. — Strong  sulfuric  acid 
and  pure  phenol  are  mixed  in  the  proportion  of 
37  grams  of  the  former  to  3  grams  of  the  latter, 
and  heated  for  six  hours  in,  not  upon,  the  water- 
bath.  The  resulting  compound  usually  solidifies 
to  a  white  mass  on  standing,  but  can  be  easily 
liquefied  on  the  water-bath  during  the  evap- 
oration of  the  samples  to  be  tested. 

The  above  method  of  preparing  the  reagent 
is  recommended  by  the  APHA,  and  is  in  general 
use  by  American  chemists.  Many  English  and 
Continental  chemists  use  a  reagent  prepared 
without  long  heating,  which  is  less  satisfactory. 
Messrs.  Chamot,  Pratt  and  Redfield  have 
shown,  however,  that  even  the  long  heating- 
first  suggested  by  Gill — does  not  produce  wholly 
satisfactory  results.  They  give  the  following  as 
an  improved  formula : 

25  grams  pure,  colorless  phenol  are  dissolved 
in  150  c.c.  of  sulfuric  acid  (sp.  gr.  1.84),  75  c.c. 
of  fuming  sulfuric  acid  (containing  not  less  than 
15  per  cent,  of  sulfuric  anhydrid)  added,  the  mix- 
ture stirred  well  and  heated  to  100°  for  two  hours. 
It  is  used  the  same  as  the  other  reagent. 


34  ANALYTIC    OPERATIONS. 

Process : 

A  measured  volume  of  the  water  is  evaporated 
just  to  dryness  in  a  porcelain  basin  about  6 
centimeters  in  diameter,  i  c.c.  of  the  phenol- 
disulfonic  acid  is  added  and  thoroughly  mixed 
with  the  residue  by  means  of  a  glass  rod.  The 
liquid  is  then  diluted  with  about  25  c.c.  of  water, 
ammonium  hydroxid  added  in  excess,  and  the 
solution  made  up  to  50  c.c. 

i  c.c.  of  the  standard  solution  of  potassium 
nitrate  is  now  similarly  evaporated  in  a  platinum 
basin,  treated  as  above,  and  made  up  to  50  c.c. 
The  color  produced  is  compared  to  that  given 
by  the  water,  and  one  or  the  other  of  the  solutions 
is  diluted  until  the  tints  of  the  two  agree.  The 
comparative  volumes  of  the  liquids  furnish  the 
necessary  data  for  determining  the  amount  of 
nitrate. 

The  results  obtained  by  this  method  are  satis- 
factory. Care  should  be  taken  that  the  same 
quantities  of  phenoldisulfonic  acid  are  used  for 
the  water  and  for  the  comparison  liquid. 

With  subsoil  and  other  waters  probably  con- 
taining much  nitrates,  10  c.c.  will  be  sufficient; 
but  with  river  and  spring  waters,  25  c.c.  may  be 
used.  When  the  organic  matter  is  sufficient  to 
color  the  residue,  it  will  be  well  to  purify  the 
water  by  addition  of  aluminum  hydroxid  and 
filtration,  before  evaporating. 


NITROGEN   AS    NITRITES.  35 

Chlorin  interferes  with  the  accuracy  of  the 
test,  but  Gill  finds  that  when  not  amounting  to 
more  than  20  parts  per  million  it  does  not  impair 
the  practical  value  of  the  results.  When  greater 
than  this,  it  is  best  to  evaporate  in  vacuo  over 
sulfuric  acid.  If  the  chlorin  be  more  than  70 
parts  per  million,  it  should  be  considerably  re- 
duced by  the  addition  of  silver  sulfate  which  has 
been  ascertained  to  be  free  from  nitrates.  Ni- 
trites do  not  influence  the  reaction. 

NITROGEN  AS  NITRITES. 

The  following  is  Ilosvay's  modification  of 
Griess's  test.  It  has  the  advantage  over  the 
original  method,  that  the  color  is  developed  more 
rapidly,  and  the  solutions  are  less  liable  to  change. 
Reagents : 

i—4-aminobenzenesulfonic  Acid  Solution  (Sul- 
fanilic  Acid). — Dissolve  0.5  gram  in  150  c.c.  of 
diluted  acetic  acid  (sp.  gr.  1.04). 

a-aminonaphthalene  Acetate  Solution. — Boil  o.i 
gram  of  solid  a-aminonaphthalene  (a-naphthyl- 
amin)  in  20  c.c.  of  water,  filter  the  solution 
through  a  plug  of  washed  absorbent  cotton, 
and  mix  the  filtrate  with  1 80  c.c.  of  diluted  acetic 
acid.  All  water  used  must  be  free  from 
nitrites,  and  all  vessels  must  be  rinsed  out  with 
such  water  before  tests  are  applied,  since  appre. 


36  ANALYTIC    OPERATIONS. 

ciable  quantities  of  nitrites  may  be  taken  up 
from  the  air. 

Standard  Sodium  Nitrite. — 0.275  gram  pure 
silver  nitrite  is  dissolved  in  pure  water,  and  a 
dilute  solution  of  pure  sodium  chlorid  added  until 
the  precipitate  ceases  to  form.  It  is  then  diluted 
with  pure  water  to  250  c.c.  and  allowed  to  stand 
until  clear.  For  use  10  c.c.  of  this  solution  are  di- 
luted to  100  c.c.  It  is  to  be  kept  in  the  dark, 
i  c.c.of  the  dilute  solution  is  equivalent  to  o.ooooi 
gram  nitrogen. 

The  silver  nitrite  is  prepared  thus :  A  hot  con- 
centrated solution  of  silver  nitrate  is  added  to  a 
concentrated  solution  of  the  purest  sodium  or 
potassium  nitrite  available,  filtered  while  hot, 
and  allowed  to  cool.  The  silver  nitrite  will 
separate  in  fine,  needle-like  crystals,  which  are 
freed  from  the  mother  liquor  by  filtration  by  the 
aid  of  a  filter  pump.  The  crystals  are  dissolved 
in  the  smallest  possible  quantity  of  hot  water, 
allowed  to  cool,  and  again  separated  by  means  of 
the  pump.  They  are  then  thoroughly  dried  in 
the  water-bath,  and  preserved  in  a  tightly  stop- 
pered bottle  away  from  the  light.  The  purity 
may  be  tested  by  heating  a  weighed  quantity 
to  redness  in  a  tared  porcelain  crucible  and  noting 
the  weight  of  the  metallic  silver.  154  parts 
should  leave  a  residue  of  108  parts  silver. 


OXYGEN-CONSUMING    POWER.  37 

Process : 

25  c.c.  of  the  water  are  placed  in  a  color-com- 
parison cylinder,  and  2  c.c.  each  of  the  test  solu- 
tions are  dropped  in.  It  is  convenient  to  have  a 
pipet  for  each  solution,  and  to  use  it  for  no  other 
purpose. 

i  c.c.  of  the  standard  nitrite  solution  is  placed 
in  another  clean  cylinder,  made  up  with  nitrite- 
free  water  to  25  c.c.  and  treated  with  the  reagents 
as  above. 

In  the  presence  of  nitrites  a  pink  color  is  pro- 
duced. At  the  end  of  five  minutes  the  two  solu- 
tions are  compared,  the  colors  equalized  by  dilut- 
ing the  darker,  and  the  calculation  made  as 
explained  under  the  determination  of  nitrates. 

OXYGEN-CONSUMING  POWER. 

All  organic  materials  being  more  or  less  easily 
oxidized,  several  methods  have  been  suggested 
for  determining  the  oxygen-consuming  powers 
of  waters  by  treatment  with  active  oxidizing 
agents.  These  methods  are,  however,  limited  in 
value.  The  organic  matters  in  water  differ  much 
in  character  and  condition,  and  their  oxidability 
is  subject  to  much  variation,  according  to  the 
circumstances  under  which  the  test  is  made. 
Nevertheless,  as  a  high  oxygen-consuming  power 
indicates  departure  from  purity,  additional  evi- 
dence may  be  obtained  by  ascertaining  it. 


38  ANALYTIC    OPERATIONS. 

It  must  not  be  overlooked  that  if  a  water  con- 
tains nitrites,  ferrous  compounds,  or  sulfur  com- 
pounds other  than  sulfates,  the  proportion  of 
oxygen  consumed  will  be  greater  than  that  re- 
quired for  the  organic  matter.  It  has  been  pro- 
posed, in  order  to  remove  the  nitrites  before 
applying  the  permanganate,  to  take  500  c.c.  of  the 
water,  add  10  c.c.  of  the  dilute  sulfuric  acid,  boil 
for  twenty  minutes,  allow  to  cool,  and  then  treat 
with  permanganate.  Since,  however,  the  amount 
of  nitrites,  if  appreciable,  can  be  directly  de- 
termined, it  is  more  satisfactory  to  deduct  from 
the  oxygen  consumed  the  amount  required  to 
convert  the  nitrites  present  into  nitrates,  and  the 
remainder  will  be  that  required  for  the  other 
oxidizable  ingredients.  14  parts  of  nitrogen  ex- 
isting as  nitrite  require  16  parts  of  oxygen  for 
conversion  into  nitrate.  Similarly,  m.8  parts 
of  iron  in  a  ferrous  compound  will  require  16 
parts  of  oxygen  for  conversion  to  the  ferric 
condition. 

Oxygen-consuming  power  may  be  determined 
indirectly  by  the  action  of  the  organic  matter 
upon  silver  compounds.  Fleck's  method  depends 
upon  the  reduction  produced  by  boiling  the  water 
with  alkaline  solution  of  silver  thiosulfate  and 
determination  of  the  unreduced  silver.  A.  R. 
Leeds  proposed  a  method  by  treating  the  water 
with  silver  nitrate,  exposing  to  light  until  it 


OXYGEN-CONSUMING   POWER.  39 

settles  perfectly  clear,  and  determining  the  re- 
duced silver. 

These  methods  are  open  to  the  same  objections 
as  in  the  use  of  permanganate,  and  do  not  seem  to 
possess  any  decided  advantage.  Qualitative  re- 
sults of  some  interest  may  occasionally  be  ob- 
tained by  the  following  method:  2  c.c.  of  a  i  per 
cent,  solution  of  silver  nitrate,  rendered  alkaline 
by  ammonium  hydroxid,  are  added  to  100  c.c.  of 
the  water  in  a  stoppered  bottle,  which  is  then 
placed  in  full  sunlight  for  two  hours.  Waters 
containing  but  little  organic  matter  will  not  show 
at  the  end  of  this  period  any  appreciable  tint. 

The  following  procedure  for  direct  oxidation  is 
recommended  by  the  APHA,  and  is  probably  as 
satisfactory  as  any  yet  proposed. 
Reagents : 

Dilute  Sulfuric  Acid. — Add  100  c.c.  of  sulfuric 
acid  to  300  c.c.  of  distilled  water,  and  potassium 
permanganate  solution  until  a  slight  pink  tint 
persists  for  several  hours. 

Standard  Potassium  Permanganate. — 0.4  gram 
of  pure  potassium  permanganate  dissolved  in 
1000  c.c.  of  water,  i  c.c.  contains  o.ooi  gram 
available  oxygen. 

Standard  Oxalate. — 0.888  crystallized  ammo- 
nium oxalate  dissolved  in  1000  c.c.  of  water,  i 
c.c.  of  this  requires  o.ooi  gram  of  oxygen  for  com- 
plete oxidation.  The  solution  should  be  com- 


40  ANALYTIC    OPERATIONS. 

pared  with  the  permanganate  solution  and  the 
exact  ratio  noted. 
Process : 

100  c.c.  of  the  sample  are  measured  into  a  flask, 
10  c.c.  each  of  the  acid  and  permanganate  solution 
added,  the  liquids  mixed  well  and  the  flask  im- 
mersed in  boiling  water,  the  level  of  which  is 
above  the  level  of  the  liquid  in  the  flask.  After 
thirty  minutes  heating,  the  flask  is  removed  from 
the  bath,  10  c.c.  of  oxalate  solution  added  and 
the  mixture  titrated  with  permanganate.  A 
blank  experiment  with  distilled  water  must  be 
made  and  the  amount  of  permanganate  deducted 
from  that  used  in  the  test ;  the  remainder  will  be 
the  permanganate  used  by  the  organic  matter. 

The  ratio  of  the  oxalate  and  permanganate  will 
usually  not  be  the  same  at  the  boiling  heat  as  in 
the  cold,  hence  the  necessity  for  frequent  verifica- 
tions of  this  ratio  under  conditions  as  near  as 
possible  to  those  of  the  actual  test. 

V 

PHOSPHATES. 

The  following  method  is  recommended  by  A.  G. 
Woodman : 
Reagents : 

Ammonium  Molybdate  Solution. — 50  grams  in 
1000  c.c.  distilled  water. 
Nitric  acid,  sp.  gr.  107. 


PHOSPHATES.  41 

Sodium  Phosphate  Solution. — 0.5324  gram  crys- 
tallized disodium  hydrogen  phosphate,  100  c.c. 
of  the  above  nitric  acid,  and  distilled  water  suffi- 
cient to  make  1000  c.c.  This  is  equivalent  to 
o.oooi  P2O5  in  i  c.c. 
Process : 

50  c.c.  of  the  sample  and  3  c.c.  of  nitric  acid  are 
evaporated  to  dryness  in  a  porcelain  dish  on  the 
water-bath,  the  residue  heated  for  two  hours  at 
100°,  and  treated  with  50  c.c.  of  cold  distilled 
water  added  in  several  portions  which  are  mixed 
in  a  comparison  tube.  It  is  usually  unnecessary 
to  filter.  4  c.c.  of  ammonium  molybdate  solu- 
tion and  2  c.c.  of  nitric  acid  are  added,  the  con- 
tents mixed,  and  after  three  minutes  the  color 
compared  with  that  given  by  different  quantities 
of  the  standard  phosphate  solution  which  have 
been  made  up  to  50  c.c.  and  the  reagents  added  in 
the  same  amount  as  above. 

Blank  tests  must  be  made  to  determine  the 
purity  of  the  materials  used.  Distilled  water 
kept  for  some  time  in  glass  vessels  may  acquire 
appreciable  amounts  of  substances  giving  color 
with  the  reagents. 

Acid  ammonium  molybdate  solution  suitable 
for  the  gravimetric  determination  of  phosphates 
may  be  prepared  as  follows : 

Weigh  into  a  beaker  10  grams  of  pure  molyb- 
denum teroxid,  mix  well  with  40  c.c.  cold  dis- 


42  ANALYTIC    OPERATIONS. 

tilled  water,  and  add  8  c.c.  strong  ammonium 
hydroxid  (sp.  gr.  0.900).  When  completely  dis- 
solved, filter  and  pour  slowly,  with  constant 
stirring,  into  a  mixture  of  40  c.c.  of  nitric  acid  (sp. 
gr.  1.42)  and  60  c.c.  of  water.  Add  0.005  gram 
sodium  ammonium  hydrogen  phosphate,  dis- 
solved in  a  little  water,  agitate  well,  allow  pre- 
cipitate to  settle  twenty-four  hours,  and  filter 
before  using. 

DISSOLVED  OXYGEN. 

Several  methods  of  different  types  have  been 
suggested  for  this  determination;  Winkler's 
method  is  preferred  by  the  APHA.  Hale  and 
Melia  have  made  investigations  of  it  and  give 
the  following  conclusions : 

It  is  very  easy,  rapid  and  accurate.  Duplicate 
samples  in  routine  work  ordinarily  check  within 
o.i  ppm.  oxygen. 

Nitrite  as  present  in  the  usual  run  of  waters  has 
no  appreciable  effect  upon  the  accuracy  of  the 
results. 

Nitrite  in  quantities  upward  of  0.2  ppm.  in- 
creases the  results  by  a  catalytic  reaction,  in- 
creasing with  increasing  amounts  of  nitrite. 

The  effect  of  high  nitrite  present  in  any  amount 
ever  occurring  in  water  may  be  counteracted  by 
the  use  of  potassium  acetate  solution  (or  sodium 


DISSOLVED   OXYGEN.  43 

acetate  crystals)  to  neutralize  the  hydrochloric 
acid  before  exposure  to  the  air.  For  the  Hale- 
Melia  procedure  for  this  case,  see  after  the  gen- 
eral procedure. 

Samples  for  oxygen  may  be  taken  and  trans- 
ported elsewhere  for  titration  in  ground  glass 
stoppered  bottles  with  part  of  the  chemicals 
added,  either  in  alkaline  or  acid  condition,  if  kept 
out  of  contact  with  air.  The  alkaline  condition 
is  preferable,  since  changes  in  temperature  can 
not  change  results,  all  the  oxygen  being  in  the 
precipitate.  In  either  condition  if  air  leaks  in  it 
may  increase  results,  in  alkaline  condition  by 
direct  absorption,  in  hydrochloric  acid  condition 
by  catalytic  action  of  nitrite.  It  is  not  advisable 
to  add  the  acetate  until  ready  for  titration. 

Samples  for  oxygen  may  best  be  transported 
elsewhere  for  determination  by  using  medicine 
pipets.  If  samples  are  not  saturated  with 
oxygen,  the  bulbs  should  be  collapsed  and  samples 
transported  without  ice;  if  supersaturated  the 
bulbs  should  be  full  of  the  water  and  samples  iced. 
Reagents : 

Manganous  Sulfate  Solution. — Dissolve  48 
grams  of  manganous  sulfate  in  100  c.c.  of  dis- 
tilled water. 

Alkaline  lodid  Solution. — Dissolve  360  grams 
of  sodium  hydroxid  and  100  grams  of  potassium 
iodid  in  1000  c.c.  of  water. 


44  ANALYTIC    OPERATIONS. 

Diluted  Sulfuric  Acid. — Strong  sulfuric  acid 
mixed  with  an  equal  volume  of  water.  The  sp. 
gr.  will  be  about  1.4. 

Sodium  Thiosulfate  Solution. — Dissolve  42 
grams  pure  re-crystallized  sodium  thiosulfate 
in  1000  c.c.  of  water.  This  is  an  N/40  solution, 
i  c.c.  of  which  is  equivalent  to  0.002  gram 
of  oxygen  (0.1395  c.c.  at  o°  and  760  mm.). 
As  the  solution  does  not  keep  well,  a  solution 
of  potassium  dichromate  of  similar  titer  should 
be  kept  for  frequent  valuation.  The  keeping 
qualities  of  the  thiosulfate  solution  are  mate- 
rially improved,  by  adding,  for  each  1000  c.c.,  5 
c.c.  of  chloroform  and  1.5  grams  of  ammonium 
carbonate  before  making  up  to  the  prescribed 
volume. 

Starch  Solution. — A  small  amount  of  good 
starch  is  stirred  with  cold  water  until  a  thin  paste 
is  produced  and  the  mixture  is  then  poured  into 
about  200  times  its  volume  of  boiling  water, 
boiled  for  a  few  minutes  and  sterilized.  It  may 
be  preserved  by  addition  of  a  few  drops  of 
chloroform. 
Process : 

Bottles  of  known  capacity  are  used,  and  the 
samples  collected  with  precautions  not  to  in- 
volve absorption  of  air.  To  the  contents  of  such 
a  bottle,  with  as  little  admission  of  air  as  possible, 
add  2  c.c.  each  of  the  manganous  sulfate  and 


DISSOLVED    OXYGEN.  45 

alkaline  iodid  solutions,  dipping  the  mouth 
of  the  pipet  below  the  surface  of  the  liquid, 
close  the  bottle,  shake,  allow  to  settle,  add 
2  c.c.  of  diluted  sulfuric  acid,  and  mix  well. 
These  manipulations  should  be  carried  on  at  the 
time  and  place  at  which  the  sample  is  collected, 
but  after  the  addition  of  the  acid  the  mixture  may 
be  transported  to  the  laboratory. 

The  contents  of  the  bottle  are  rinsed  into  a 
flask  and  titrated  with  sodium  thiosulfate  solu- 
tion, adding,  when  the  liquid  becomes  faintly 
yellow,  a  few  c.c.  of  starch  solution  as  an 
indicator. 

Hale  and  Melia  recommend  the  following  pro- 
cedure for  waters  rich  in  nitrites :  Add,  at  the  bot- 
tom of  the  bottle,  2  c.c.  of  the  manganous  sulfate 
solution,  followed  by  2  c.c.  of  the  alkaline  iodid 
solution.  Shake,  allow  to  settle,  introduce  to 
the  bottom  of  the  liquid  2  c.c.  of  concentrated 
hydrochloric  acid  and  shake  until  the  precipitate 
is  entirely  dissolved.  Then  add  2  c.c.  of  potas- 
sium acetate  solution  (100  grams  to  100  c.c.). 
Shake,  allow  to  settle,  add  at  the  bottom  2  c.c. 
concentrated  hydrochloric  acid  and  shake  until 
the  precipitate  is  entirely  dissolved.  Add  2  c.c. 
potassium  acetate  solution  (100  grams)  at  the 
bottom  and  mix.  Withdraw  by  pipet  100  c.c. 
into  an  Erlenmeyer  flask  and  titrate  with  N/IO 
thiosulfate,  adding  a  little  starch  solution  at  the 


46  ANALYTIC    OPERATIONS. 

end.  Correction  must  be  made  for  6  c.c.  of  water 
displaced  by  the  first  two  solutions  and  by  the 
acetate  solution.  The  acid  needs  no  correction, 
since  it  displaces  only  water  from  which  oxygen 
has  been  removed. 

Precautions  must  be  taken  to  exclude  contact 
with  air  as  much  as  possible  until  the  solution  is 
ready  to  titrate  by  replacing  the  stopper  as 
quickly  as  possible  after  each  reagent  is  intro- 
duc,ed;  to  get  complete  solution  of  the  precipitate 
by  the  hydrochloric  acid;  to  give  the  thiosulfate 
a  little  more  time  to  react  at  the  end  point  in  the 
acetic  acid  condition;  to  use  small  amounts  of 
starch  solution.  For  introducing  the  solutions  it 
is  advisable  to  use  pi  pets  with  two  marks,  measur- 
ing 2  c.c.,  well  up  on  the  pipet  so  as  to  give  head 
and  not  contaminate  the  upper  liquid  in  the  bottle 
more  than  necessary  while  actually  displacing 
liquid  from  the  bottle  in  proportion  to  the  amount 
introduced. 

The  amount  of  oxygen  is  best  stated  in  parts 
per  million  by  weight,  but  it  is  sometimes  desired 
to  give  it  in  c.c.  for  a  given  volume  of  the  water. 
The  following  formulas,  given  by  the  APHA,  are 
used  in  which  n  —  number  of  c.c.  of  thiosulfate 
solution  used,  and  v  —  the  capacity  of  the  bottle, 
less  4,  deducted  for  the  displacement  by  the 
reagent. 


HARDNESS.  47 

200n 

=  ppm.  of  oxygen  in  sample. 

=  c.c.  of  oxygen  at  o°  and  760  mm.,  in 
1000  c.c.  of  sample. 

HARDNESS. 

Water  containing  notable  amounts  of  calcium 
and  magnesium  carbonates  is  termed  "hard," 
the  practical  importance  of  the  condition  being 
mainly  the  liability  to  form  scale  in  boilers,  and 
to  interfere  with  the  formation  of  lather  with 
soap ;  in  fact,  the  soap-consuming  power  is  usually 
intended  by  the  term.  Hardness  may  be  caused 
by  many  substances,  but  the  common  causes  are 
calcium  and  magnesium  carbonates  and  sulfates, 
occasionally  the  chlorids  and,  rarely,  the  other 
halids.  Magnesium  sulfate  is  freely  soluble  in 
water,  calcium  sulfate  slightly  so,  but  the  car- 
bonates are  almost  insoluble.  Natural  waters, 
however,  generally  contain  notable  amounts  of 
carbonic  acid,  and  this  has  a  marked  solvent  action 
on  the  carbonates.  When  waters  thus  charged 
with  carbonates  are  boiled  or  freely  exposed  to  the 
air,  much  of  the  carbonic  acid  is  driven  of,  the 
carbonates  precipitate  and  are  not  re-dissolved 
on  cooling.  On  the  other  hand,  the  sulfates  and 
chlorids  are  not  precipitated  by  boiling  or  ex- 


48  ANALYTIC    OPERATIONS. 

posure  to  air,  hence  chemists  distinguish  between 
"temporary"  and  "permanent"  hardness,  the 
former  being  that  due  to  carbonates  held  in  solu- 
tion by  carbonic  acid.  The  APHA  proposes  the 
term  "non-carbonate"  as  a  substitute  for  "per- 
manent" in  this  connection.  Hardness  may  be 
determined  in  several  ways.  A  gravimetric 
analysis  will  give  accurately  the  substances  pres- 
ent, but  it  is  too  tedious  for  ordinary  routine. 
The  amount  of  soap  required  to  make  a  persisting 
lather  with  a  given  volume  of  the  water  may  be 
measured;  titration  with  standard  acid  will  de- 
termine the  carbonates,  and,  by  a  simple  modifi- 
cation, the  sulfates  (and  halogen  salts)  may  be 
ascertained.  Both  these  methods  are  much  in 
vogue. 

TITRATION  METHOD. — This  is  due  to  Hehner, 
whose  procedure  with  slight  modifications  is  still 
in  use.     The  solutions  are: 
N/so  Sodium  Carbonate. — 1.062  grams  pure  dry  so- 
dium carbonate  dissolved  in  1000  c.c.  of  water. 
N/so  SulfuricAcid.—**/IO  acid  is  diluted  with  four 
times  its  volume  of  water. 

Temporary  Hardness  (APHA  Procedure) — 100 
c.c.  of  the  sample  are  placed  in  a  porcelain  basin, 
0.5  c.c.  of  lakmoid  solution  (o.i  gram  to  50  c.c. 
of  50  per  cent,  alcohol)  added  and  the  sulfuric 
acid  run  in  until  the  amount  is  close  to  the 
neutralizing  point.  The  liquid  is  then  heated 


HARDNESS.  49 

until  bubbles  of  steam  just  begin  to  break  on 
the  surface,  the  heat  is  withdrawn  and  titration 
continued  until  a  drop  of  the  acid  produces  no 
change  in  sinking  in  the  liquid.  The  number 
of  c.c.  used  multiplied  by  10  gives  the  parts  per 
million  of  alkalinity  in  terms  of  calcium  carbonate. 

Erythrosin  G  (iodeosin  G,  sodium  salt  of 
tetriodofluorescein)  is  preferred  by  many  ana- 
lysts as  an  indicator.  R.  Haines  has  furnished 
some  data  on  the  subject.  The  common  ery- 
throsins,  such  as  B  and  BB,  used  for  staining,  are 
unsuited  on  account  of  their  fluorescence  which 
confuses  the  end  point.  Methyl  orange  is  dis- 
approved by  the  APHA.  If  used,  it  should  be  in 
very  dilute  solution  and  not  above  40°.  Ery- 
throsin is  applied  by  the  APHA  as  follows: 

100  c.c.  of  the  sample  are  placed  in  a  bottle  or 
flask  holding  250  c.c.,  2  c.c.  of  erythrosin  solution 
(i  gram  to  1000  c.c.  of  pure  water)  and  5  c.c.  of 
chloroform  added,  and  the  liquid  titrated  with 
the  sulfuric  acid,  shaking  well  between  each 
addition.  The  rose  tint  of  the  indicator  gradu- 
ally diminishes  and  is  finally  discharged  by  a  drop 
or  two  of  the  acid,  which  is  the  end  point.  The 
chloroform  must  be  neutral  to  the  indicator. 
The  data  have  the  same  significance  as  with 
lakmoid. 

Permanent  (Non-carbonate)  Hardness. — Hehner's 
method  is  still  much  in  vogue,  with  some  modifi- 
4 


50  ANALYTIC    OPERATIONS. 

cations :  To  100  c.c.  of  the  sample,  sufficient  of  the 
sodium  carbonate  solution  is  added  to  convert  the 
calcium  and  magnesium  present  into  carbonates. 
Generally,  i  c.c.  for  each  10  parts  per  million  of 
solids  in  the  water  will  be  satisfactory.  The  mix- 
ture is  evaporated  to  dryness,  the  residue  ex- 
tracted with  a  little  recently  boiled  distilled  water, 
filtered — using  a  very  small  filter — and  washed 
with  small  portions  of  water  several  times.  The 
filtrates  are  mixed  and  titrated  hot  with  the 
acid.  The  c.c.  of  acid  used  are  deducted  from 
the  c.c.  of  carbonate  solution  added;  the  remain- 
der is  the  parts  per  million  of  non-carbonate 
hardness. 

Owing  to  the  liability  of  glass  and  porcelain  to 
yield  alkali,  the  evaporation  is  best  conducted  in 
platinum  or  nickel,  but  Jena  glass  may  in  many 
cases  be  used. 

If  the  water  contains  sodium  or  potassium  car- 
bonate, there  is  no  permanent  hardness,  and  more 
acid  will  be  required  for  the  filtrate  than  the 
equivalent  of  the  sodium  carbonate  added. 
From  this  excess  the  quantity  of  sodium  carbon- 
ate in  the  water  may  be  determined. 

In  such  case,  since  any  alkali  carbonate  in  the 
water  would  be  erroneously  calculated  as  tem- 
porary hardness  by  the  direct  titration,  the 
equivalent,  in  terms  of  calcium  carbonate,  of  the 
alkali  carbonate  present  should  be  deducted  from 


HARDNESS.  51 

the  figure  given  by  the  first  titration  in  order  to 
get  the  true  temporary  hardness. 

APHA  Method  for  Non-carbonate  Hardness. — 
This,  devised  by  Pfeifer  and  Wartha,  employs  for 
precipitating  the  calcium  and  magnesium  a  so- 
called  "soda-reagent,"  equal  volumes  of  N/IO 
sodium  hydroxid  and  sodium  carbonate. 

200  c.c.  of  the  sample  are  placed  in  a  Jena  flask, 
boiled  ten  minutes,  to  expel  carbonic  acid,  and 
25  c.c.  of  the  soda-reagent  added.  The  mixture 
is  concentrated  to  100  c.c.,  cooled,  transferred 
to  a  200-c.c.  flask,  made  up  to  the  mark  with 
boiled  distilled  water,  and  filtered  (dry  filter). 
The  first  50  c.c.  are  rejected;  100  c.c.  of  the  next 
portions  are  titrated  with  standard  acid  using 
erythrosin  G  as  an  indicator. 

The  APHA  recommends  N/20  acid,  and  with  this 
the  formula  for  calculation  of  results  is  %  =  12.5 
(s  —  2n)  in  which  5  is  the  c.c.  of  acid  equivalent 
to  the  soda-reagent  used,  n  the  c.c.  required  for 
the  titration,  and  x  the  non-carbonate  hardness 
in  parts  per  million  of  calcium  carbonate.  This 
formula  can  easily  be  adapted  for  any  other 
strength  of  acid. 

Total  hardness  may  also  be  determined  by  this 
method.  200  c.c.  of  the  sample  are  mixed  with 
just  sufficient  standard  acid  to  neutralize  the 
alkalinity.  The  carbonates  are  converted  into 
sulfates.  The  mixture  is  boiled  to  100  c.c., 


52  ANALYTIC    OPERATIONS. 

cooled,  mixed  with  25  c.c.  of  soda-reagent,  again 
concentrated  to  100  c.c.,  cooled,  made  up  to 
200  c.c.,  titrated  with  acid  and  computed  as 
above.  The  non-carbonate  hardness  is  obtained 
by  subtracting  the  alkalinity  from  the  total 
hardness. 

SOAP  METHOD. — Many  chemists  estimate  hard- 
ness by  the  use  of  soap  solution,  but  the  procedure, 
at  best,  is  inferior  in  accuracy.  The  following 
is  essentially  the  method  given  by  the  APHA. 

Calcium  Chlorid  Solution. — 0.2  gram  pure  dry 
calcium  carbonate  is  dissolved  in  a  little  pure 
dilute  hydrochloric  acid,  care  being  taken  to  avoid 
loss  by  spattering.  The  liquid  is  evaporated  to 
dryness,  re-dissolved  in  a  little  water  and  again 
evaporated,  this  operation  being  repeated  several 
times  to  ensure  the  removal  of  the  excess  of  acid. 
The  residue  is  dissolved  finally  and  made  up  to 
loooc.c.  i  c.c.  =  0.0002  gram  calcium  carbonate. 

Soap  Solution. — Dissolve  25  grams  of  fine 
white  Castile  soap  in  250  c.c.  of  80  per  cent,  alco- 
hol. Allow  the  solution  to  stand  several  days, 
decant  a  convenient  quantity  and  dilute  with 
70  per  cent,  alcohol  to  such  a  volume  that  6.4 
c.c.  will  just  make  a  permanent  lather  with 
20  c.c.  of  the  calcium  chlorid  solution,  following 
the  technic  described  below.  Usually  from  75  to 
100  c.c.  of  the  strong  solution  will  be  required 
to  make  1000  c.c.  of  the  dilute  standard.  The 


HARDNESS.  53 

latter  solution  must  be  titrated  from  time  to  time 
with  the  calcium  chlorid  solution  to  detect  any 
change  of  ratio. 

The  term  "Castile"  as  applied  to  soap  has  now 
no  definite  value;  any  manufacturer  may  use  it. 
It  is  best,  therefore,  to  use  commercial  oleic  acid 
now  obtainable  of  good  quality  and  saponify 
cautiously  with  good  sodium  hydroxid. 

The  procedure  with  soap  solution  is  as  follows : 

50  c.c.  of  the  sample  are  placed  in  a  25o-c.c. 
flask,  and  the  soap  solution  added  in  portions  of 
not  more  than  0.3  c.c.  at  a  time,  shaking  well  be- 
tween each  addition.  When  a  lather  forms  over 
the  whole  surface  of  the  water  and  remains  sub- 
stantially unchanged  for  five  minutes  while  the 
flask  lies  on  its  side,  the  buret  should  be  read. 

The  soap  solution  must  be  added  in  small 
portions,  especially  in  presence  of  notable  amounts 
of  magnesium  compounds.  If  much  carbonic 
acid  is  present  it  is  an  advantage  to  remove  some 
of  it  by  suction  with  a  filter  pump,  taking  care, 
of  course,  not  to  cause  precipitation  of  carbon- 
ates. If  the  sample  requires  more  than  7.9  c.c. 
of  soap  solution,  a  smaller  volume,  25  c.c.,  10  c.c., 
sometimes  even  2  c.c.,  must  be  diluted  with  re- 
cently boiled  distilled  water  and  the  test  repeated, 
but  the  results  in  such  cases  will  be  less  accurate. 

DEGREES  OF  HARDNESS. — Hardness  tests  are 
often  reported  under  this  term,  which  should  be 


54 


ANALYTIC    OPERATIONS. 


abandoned.  The  standards  differ  in  different 
nations. 

English  degrees  (Clark's  scale)  are  the  equiva- 
lent in  grains  per  Imperial  gallon,  and  must  be 
multiplied  by  14.3  to  convert  them  to  parts  per 
million. 

French  degrees  represent  parts  per  100,000  and 
are  converted  to  parts  per  million  by  multiplying 
by  10. 


C.c. 
SOAP 
SOLU- 
TION 

0.8 

0.9 

.o 


9 
.o 

2.1 
2.2 

2-3 
2.4 

I.I 

1:1 

2.9 
30 


HARD- 

NESS 

1.6 

M 

6.3 

79 

95 

n. i 

12.7 
14-3 

iS.'? 

19  5 
20.8 

22.1 

23  4 
24.7 
26.0 

III 

29  9 
31.2 
32.5 
33-8 


C.c. 

SOAP 

SOLU- 

TION 

32 
33 
3-4 


M 

39 
4.0 

4-1 
4.2 

4-3 
4.4 


49 
50 

5-1 
5-2 
53 
5-4 
55 


HARD- 
NESS 


36.4 
37-7 
38.0 

40.3 
41.6 
42.9 
44-3 
45-7 


50.0 

51.4 

52.9 

54 

55 

57 


62.9 
64.3 
65.7 
67.1 


C.c. 

SOAP 

HARD 

SOLU- 

NESS 

TION 

56 

68.6 

57 

70.0 

5-8 

71.4 

5-9 

72.9 

6.0 

74-3 

6.1 

75-7 

6.2 

6-3 

78.6 

6.4 

80.0 

6-5 
6.6 

81.4 
83  9 

6.7 
6.8 

84.3 
85.7 

6.9 

87-1 

7.0 

88.6 

7-1 

90.0 

72 

91.4 

7-3 

92.9 

7-4 

94  3 

7.5 

95-7 

76 

97.1 

7-7 

98.6 

7-8 

IOO.O 

7-9 

101.5 

German  degrees  represent  parts  per  100,000  of 


POISONOUS    METALS.  55 

calcium  oxid,  and  are  to  be  multiplied  by  17.8 
to  obtain  parts  per  million  of  calcium  carbonate. 

Of  course,  degrees  of  either  type  may  be  ob- 
tained by  dividing  the  figure  for  parts  per  million 
by  the  above  factors  respectively. 

The  table  on  page  54  gives  the  parts  per  million 
of  calcium  carbonate,  or  its  equivalent  in  soap- 
precipitating  power,  corresponding  to  the  amount 
of  soap  solution  used. 

POISONOUS  METALS. 

Under  this  conventional  title  are  included 
barium,  chromium,  zinc,  arsenic,  copper,  and  lead; 
manganese,  iron,  aluminum,  also,  though  not 
usually  classed  in  this  group,  are  objectionable 
when  present  in  notable  amounts. 

In  the  commercial  laboratory,  in  which  water 
samples  from  many  different  places  are  examined, 
it  is  convenient  to  have  a  routine  general  test  for 
metals  precipitable  as  sulfids.  This  is  most 
conveniently  done  by  adding  to  a  small  volume 
of  the  water,  in  a  colorless  glass  vessel,  a  drop 
or  two  of  ammonium  (or  sodium)  sulfid.  A  dis- 
tinct precipitate,  unless  due  to  iron,  will  indicate 
a  poisonous  metal.  A  mere  opalescence  may  be 
neglected,  as  it  is  due  to  separated  sulfur.  The 
iron  present  in  ordinary  waters  is  not  usually 
sufficient  to  give  a  precipitate.  The  water  must 


56  ANALYTIC    OPERATIONS. 

not  be  acid  when  making  the  test.  Care  must 
be  taken  not  to  mistake  white  zinc  sulfid  for  the 
sulfur  precipitated  by  the  oxidizing  action  of  the 
air  in  the  water  on  the  alkaline  sulfid. 

Barium  is  rarely  present,  and  only  in  water 
containing  no  sulfates.  It  can  be  detected  by 
slightly  acidifying  the  water  with  hydrochloric 
acid,  filtering  if  necessary,  and  adding  solution 
of  calcium  sulfate.  The  precipitated  barium 
sulfate  may  be  collected  and  weighed. 

Chromium  is  rarely  present,  but  may  be  looked 
for  in  the  waste  waters  of  dye-works  and  similar 
sources.  To  detect  it,  a  considerable  volume  of 
the  water  is  evaporated  to  dryness  with  addition 
of  a  small  amount  of  potassium  chlorate  and 
nitrate,  transferred  to  a  porcelain  crucible  and 
brought  to  quiet  fusion;  any  chromium  present 
will  be  found  in  the  residue  in  the  form  of  chrom- 
ate.  The  fused  mass,  after  cooling,  is  boiled 
with  a  little  water,  filtered,  the  filtrate  rendered 
slightly  acid  with  hydrochloric  acid,  and  a  solu- 
tion of  hydrogen  dioxid  added.  In  the  presence 
of  chromium  a  transient  blue  color  will  appear; 
by  adding  a  little  ether  and  shaking  the  mixture, 
the  color  will  pass  into  the  ether,  and  on  standing 
will  form  a  blue  layer  on  the  surface  of  the  water. 

Zinc  is  best  detected  by  the  test  described  by 
Allen.  The  water  is  rendered  slightly  alkaline  by 
addition  of  ammonium  hydroxid,  heated  to  boil- 


POISONOUS    METALS.  57 

ing,  filtered,  and  the  clear  liquid  treated  with  a 
few  drops  of  potassium  ferrocyanid;  in  the  pres- 
ence even  of 'the  merest  trace  of  zinc  a  white 
precipitate  will  be  produced. 

Arsenic  is  most  readily  detected  by  Reinsch's 
test.  1000  c.c.  of  the  water  is  rendered  slightly 
alkaline  by  pure  sodium  carbonate,  and  evapo- 
rated nearly  to  dryness  in  a  porcelain  basin.  2 
or  3  c.c.  of  water  strongly  acidulated  with  hy- 
drochloric acid  are  placed  in  a  small  test-tube, 
about  y^,  of  a  square  centimeter  of  bright  copper 
foil  is  added,  and  the  liquid  boiled  gently  for  a  few 
moments.  If  the  copper  remains  bright,  showing 
that  the  reagents  contain  no  arsenic,  the  water- 
residue  is  acidified  with  hydrochloric  acid,  added 
to  the  contents  of  the  test-tube,  and  the  liquid 
again  boiled  for  several  minutes.  If  arsenic  be 
present,  a  steel-gray  stain  will  appear  on  the 
copper.  The  slip  is  removed,  washed  with  dis- 
tilled water,  thoroughly  dried  by  pressure  between 
filter  paper,  inserted  into  a  narrow  glass  tube 
closed  at  one  end,  which  has  been  previously 
dried  by  heating  nearly,  to  redness.  The  tube 
is  gently  heated  at  the  point  at  which  the  copper 
rests;  the  deposit  will  sublime  and  collect  on  the 
cooler  portion  of  the  tube,  in  crystals  which  the 
microscope  shows  to  be  octahedral. 

Since  small  amounts  of  arsenic  frequently 
occur  in  reagents  and  in  glass  vessels,  care  must 


58  ANALYTIC    OPERATIONS. 

be  taken  to  avoid  such  sources  of  error.  Sodium 
carbonate  solution  may  contain  arsenic  dissolved 
from  the  glass  bottle  in  which  it  is  kept.  It  is 
best,  therefore,  to  use  the  solid  carbonate  for 
rendering  the  water  alkaline,  and  to  determine 
its  purity  before  use. 

Iron  is  detected  by  the  addition  of  a  drop  of 
ammonium  sulfid  to  the  water  in  a  tall,  glass 
cylinder.  Ferrous  sulfid  is  formed,  having  a 
greenish-black  color,  instantly  discharged  by 
acidifying  the  water  with  dilute  hydrochloric 
acid.  A  still  better  test  is  the  production  of  a 
blood-red  color,  with  potassium  thiocyanate,  due 
to  the  formation  of  ferric  thiocyanate.  The 
water  should  be  first  boiled  with  a  few  drops  of 
nitric  acid,  to  convert  the  iron  to  the  ferric  con- 
dition, cooled,  and  a  drop  or  two  of  the  solution 
of  potassium  thiocyanate  added.  The  test  is 
very  delicate. 

DETERMINATION. — The  following  method  was 
devised  by  Thompson  and  is  described  in  Sutton's 
1 '  Volumetric  Analysis : ' ' 

Standard  Ferric  Sulfate. — 0.7  gram  ferrous 
ammonium  sulfate  is  dissolved  in  water  acidified 
with  sulfuric  acid,  and  potassium  permanganate 
solution  added  until  the  solution  turns  a  very 
faint  pink  color.  The  solution  [is*  [diluted  to 
1000  c.c.  i  c.c.  contains  o.i  milligram  iron. 


POISONOUS    METALS.  59 

Diluted  Nitric  Acid. — 30  c.c.  concentrated 
nitric  acid  diluted  with  water  to  about  100  c.c. 

Potassium  Thiocyanate. — 5  grams  of  the  salt 
dissolved  in  about  100  c.c.  water. 

100  c.c.  of  the  water  are  evaporated  to  small 
bulk,  acidified  with  hydrochloric  acid,  and  just 
sufficient  dilute  potassium  permanganate  solution 
added  to  convert  all  the  iron  to  the  ferric  condi- 
tion. The  liquid  is  evaporated  nearly  to  dryness 
to  drive  off  excess  of  acid,  then  diluted  to  its 
original  volume,  100  c.c.  In  two  tall  glasses 
marked  at  100  c.c.,  5  c.c.  of  the  nitric  acid  and  15 
c.c.  of  the  thiocyanate  solution  are  placed.  To 
one  of  these  a  measured  volume  of  the  treated 
water  is  added  and  both  vessels  filled  up  to  the 
mark  with  distilled  water.  If  iron  is  present, 
a  blood-red  color  will  be  produced.  Standard 
iron  solution  is  added  to  the  second  vessel  until 
the  color  agrees.  The  amount  of  water  which  is 
added  to  the  first  glass  will  depend  upon  the  quan- 
tity of  iron  it  contains;  not  more  should  be 
used  than  will  require  2  or  3  c.c.  of  the  standard 
to  match  it,  otherwise  the  color  will  be  too  deep 
for  comparison. 

Manganese. — The  following  method  is  de- 
scribed by  Wanklyn  in  his  treatise  on  water  anal- 
ysis. About  1000  c.c.  of  the  water  is  evaporated 
to  small  bulk,  nearly  neutralized  by  hydrochloric 
acid  and  treated  with  a  few  drops  of  a  solution 


60  ANALYTIC    OPERATIONS. 

of  hydrogen  dioxid.  The  formation  of  a  brown 
precipitate  indicates  the  presence  of  manganese. 
The  test  is  very  delicate.  The  precipitate  may 
be  collected  on  a  filter,  the  filter  ashed,  and  the 
residue  fused  with  a  mixture  of  sodium  carbonate 
and  potassium  nitrate.  Green  potassium  manga- 
nate  will  be  produced,  which,  when  boiled  with 
water,  will  give  a  bright-red  solution  of  potassium 
permanganate.  The  quantitative  determination 
is  given  elsewhere. 

Aluminum. — Traces  of  this  element  are  to  be 
expected  in  all  waters,  and  it  is  not  usual  to  test 
for  it  except  in  elaborate  analysis  of  the  mineral 
ingredients,  as  described  in  another  section.  The 
use  of  aluminum  sulfate  as  a  coagulant  in  many 
rapid-filtration  methods  makes  it  necessary  to 
examine  effluents  for  excess  of  precipitant.  As 
the  precipitating  power  depends  on  the  reaction 
with  carbonates,  the  alkalinity  of  the  water  is 
diminished  in  proportion  to  the  amount  of  alumi- 
num compounds  decomposed,  hence  if  the  latter 
is  in  excess  the  water  will  be  acid  to  many  indica- 
tors. Quantitative  tests  may  be  made  by  titrat- 
ing with  lakmoid,  phenacetolin,  or  erythrosin  G. 
Methyl  orange  is  not  suitable.  LefTmann  has 
found  that  sodium  alizarin-monosulfonate  has 
a  special  action  in  the  presence  of  excess  of  alumi- 
num compounds.  This  indicator  is  red  when  alka- 
line, yellow  when  acid,  but  in  water  containing 


POISONOUS    METALS.  6l 

aluminum  sulf ate  it  assumes  an  intermediate  tint 
which  a  moderate  excess  of  mineral  acid  does  not 
affect. 

Lead  may  be  readily  detected  by  adding  to  the 
water  in  a  tall  glass  cylinder  a  drop  of  ammonium 
sulfid ;  brownish-black  lead  sulfid  is  formed,  which 
does  not  dissolve  either  by  acidulating  the  water 
with  dilute  hydrochloric  acid  (distinction  from 
iron),  nor  by  the  addition  of  about  i  c.c.  of  a 
strong  solution  of  potassium  cyanid  (distinction 
from  copper).  As  a  delicate  test,  S.  Harvey  gives 
the  following  method:  250  c.c.  of  the  sample  are 
placed  in  a  precipitating  jar,  about  o.i  gram  of 
crystallized  potassium  dichromate  is  added  and 
dissolved  by  agitation.  The  same  volume  of  lead- 
free  water  is  treated  in  the  same  manner,  and  the 
two  liquids  compared  side  by  side.  Water  con- 
taining 0.3  part  per  million  will  show  a  turbidity 
in  fifteen  minutes  which  will  be  rendered  more  dis- 
tinct by  contrast  with  the  clear  water  alongside. 
By  allowing  the  jar  to  stand  for  about  twelve 
hours  undisturbed,  the  precipitate  will  settle  and 
will  become  still  more  distinct.  No  other  metal 
likely  to  be  present  in  water  will  give  a  similar 
reaction. 

In  the  absence  of  copper,  lead  may  be  deter- 
mined as  follows :  A  solution  is  prepared  contain- 
ing 0.16  gram  of  lead  nitrate  to  100  c.c.;  i  c.c. 
of  this  contains  o.ooi  gram  lead.  100  c.c.  of  the 


62  ANALYTIC    OPERATIONS. 

water  to  be  tested  are  placed  in  a  tall  glass  vessel, 
made  acid  by  the  addition  of  a  few  drops  of  acetic 
acid,  and  5  c.c.  of  hydrogen  sulfid  added.  In  a 
similar  vessel  100  c.c.  of  distilled  water  are  placed, 
together  with  the  same  quantities  of  acetic  acid 
and  hydrogen  sulfid,  and  sufficient  of  the  standard 
lead  solution  to  match  the  tint  in  the  first  cylinder. 
The  amount  of  lead  in  the  water  under  examina- 
tion is  thus  known. 

Copper  is  detected  in  the  same  manner  as  lead 
by  acidifying  the  water  with  acetic  acid  and  add- 
ing hydrogen  sulfid.  The  precipitate  is  distin- 
guished from  lead  sulfid  by  the  fact  that  the  color 
is  discharged  on  the  addition  of  about  i  c.c.  of  a 
strong  solution  of  pure  potassium  cyanid.  It  may 
be  further  confirmed  by  the  addition  to  another 
portion  of  the  water  of  a  solution  of  potassium 
ferrocyanid.  In  the  presence  of  even  a  very 
small  amount  of  copper,  a  mahogany-red  is 
produced. 

In  the  absence  of  lead,  copper  is  determined  in 
the  same  way  as  that  metal,  using  a  standard 
solution  of  copper  for  the  comparison  liquid, 
made  by  dissolving  3.929  grams  of  crystallized 
copper  sulfate  in  1000  c.c.  of  water,  i  c.c.  of  the 
solution  contains  i  gram  copper. 

H.  C.  Bradley  states  that  hematoxylin  (from 
logwood)  is  a  delicate  test  for  copper.  It  is  best 
used  in  weak  alcoholic  solution  to  which  a  trace 


GENERAL  QUANTITATIVE    ANALYSIS.  63 

of  sodium  hydroxid  has  been  added,  which  renders 
the  liquid  faintly  pink.  A  few  drops  of  this  rea- 
gent will  in  the  course  of  a  few  minutes  give  a 
distinct  blue  even  with  very  small  amounts  of 
copper.  Moderate  amounts  produce  a  precipi- 
tate. The  liquid  should  stand  for  an  hour  or  so 
before  deciding  that  the  result  is  negative.  Free 
mineral  acid  interfere  with  the  test. 

If  both  lead  and  copper  are  present,  a  large 
quantity  of  the  water  should  be  evaporated  to 
small  bulk,  and  the  metals  separated  by  one  of 
the  standard  laboratory  methods. 

As  copper  sulfate  is  much  used  to  prevent 
growth  of  algae,  it  is  advisable  to  test  for  it  in 
surface  waters. 

GENERAL  QUANTITATIVE  ANALYSIS. 

Silica,  Iron,  Aluminum,  Manganese,  Calcium, 
and  Magnesium. — A  considerable  volume  of  the 
sample  (in  case  of  water  containing  only  moderate 
amounts  of  solids,  at  least  1000  c.c.)  is  evaporated 
to  small  bulk,  rendered  acid  with  dilute  hydro- 
chloric acid,  the  evaporation  carried  to  dryness, 
the  residue  heated  briefly  to  180°,  or  baked  for 
thirty  minutes  at  about  1 10°  on  an  asbestos  plate, 
treated  with  a  little  dilute  hydrochloric,  again 
evaporated  to  dryness,  some  strong  hydrochloric 
acid  added,  diluted,  the  mixture  filtered,  and  the 


64  ANALYTIC    OPERATIONS. 

separated  silica  washed,  dried,  ignited  in  a  plati- 
num crucible,  and  weighed. 

To  the  filtrate,  previously  boiled  with  a  few 
drops  of  strong  nitric  acid,  excess  of  ammonium 
hydroxid  is  added,  the  liquid  boiled  several 
minutes,  the  precipitate  collected,  washed  with 
boiling  water,  dried,  ignited,  and  weighed.  It 
consists  of  Fe2O3  and  AUOa;  also  all  the  phos- 
phates and  some  manganese  if  much  of  the  latter 
is  present  in  the  water.  In  such  cases  the  pre- 
cipitate before  drying  is  redissolved  in  hydro- 
chloric acid  and  neutralized  with  a  dilute  solution 
of  ammonium  carbonate  until  the  water  becomes 
almost  turbid.  It  is  then  boiled,  and  the  pre- 
cipitate, now  free  from  manganese,  washed,  dried, 
ignited,  and  weighed.  The  iron  may  be  deter- 
mined by  dissolving  the  precipitate  in  strong 
hydrochloric  acid  and  employing  the  colorimetric 
method  described  on  page  58. 

If  no  manganese,  or  only  traces  are  present,  the 
filtrate  from  the  ammoniacal  solution  is  heated 
to  a  moderate  temperature,  and  strong  solution  of 
ammonium  oxalate  added  in  small  portions  with 
stirring,  until  the  precipitate  tends  to  settle 
readily  and  leave  the  liquid  clear.  The  precipi- 
tate is  collected  on  a  filter  and  washed.  It  is  cal- 
cium oxalate  only,  if  but  little  magnesium  is  pres- 
ent in  the  water,  but  if  the  proportion  of  magne- 
sium is  large  some  magnesium  oxalate  may  be 


GENERAL  QUANTITATIVE    ANALYSIS.  65 

also  thrown  down.  In  this  case,  the  precipitate 
should  be  dissolved  in  a  minimum  quantity  of 
hot  strong  hydrochloric  acid,  the  solution  diluted 
with  water,  excess  of  ammonium  hydroxid  and  a 
small  quantity  of  ammonium  oxalate.  After  the 
precipitate  has  completely  subsided,  it  is  collected 
on  a  filter,  washed  and  dried.  If  quite  small  in 
amount,  it  is  placed  with  the  filter  in  a  weighed 
platinum  crucible,  ignited  over  the  Bunsen  burner 
for  a  short  time,  and  then  over  the  blast  lamp  for 
from  five  to  fifteen  minutes.  Calcium  oxid  is 
thus  obtained;  it  is  allowed  to  cool  in  the  desic- 
cator and  weighed.  The  weight  multiplied  by 
0.715  gives  the  weight  of  calcium.  When  the 
amount  of  precipitate  is  large,  it  is  better  to  re- 
move it  from  the  filter,  and  heat  it  just  short  of 
redness  until  it  assumes  a  grayish  tint.  It  then 
consists  of  calcium  carbonate.  To  this  is  added 
the  ash  of  the  filter.  The  weight  of  the  calcium 
carbonate  multiplied  by  0.4  gives  the  weight  of 
calcium. 

Calcium  may  be  also  determined  by  titration. 
The  precipitate  of  calcium  oxalate,  after  thorough 
washing,  is  dissolved  from  the  filter  by  warm, 
dilute,  sulfuric  acid,  heated  to  about  65°,  and 
titrated  with  decinormal  permanganate  until  a 
pink  tint  is  obtained,  i  c.c.  of  the  permanganate 
is  equivalent  to  0.002  gram  calcium;  0.0028  cal- 
cium oxid;  0.0050  calcium  carbonate. 
5 


66  ANALYTIC    OPERATIONS. 

The  filtrates  from  the  calcium  oxalate  are  mixed, 
slightly  acidified  with  hydrochloric  acid,  concen- 
trated and  cooled,  ammonium  hydroxid  and  so- 
dium phosphate  added  in  excess,  stirred  briskly 
and  allowed  to  stand  in  the  cold  for  about  twelve 
hours.  The  precipitated  ammonium  magnesium 
phosphate  is  brought  upon  a  filter,  that  adhering 
to  the  sides  of  the  vessel  being  dislodged  by  rub- 
bing with  a  glass  rod  tipped  with  a  piece  of  clean 
rubber  tubing.  It  is  washed  with  a  solution  made 
by  mixing  i  part  of  the  ammonium  hydroxid  of 
0.96  sp.  gr.  with  3  parts  of  water.  The  pre- 
cipitate is  dried,  transferred  to  a  platinum  cruci- 
ble, the  filter  ashed  separately  and  added  to  it, 
and  the  whole  heated  at  first  gently  and  then 
to  intense  redness  for  several  minutes.  After 
cooling,  it  is  weighed.  It  consists  of  magnesium 
pyrophosphate ;  the  weight  multiplied  by  0.218 
gives  the  weight  of  magnesium. 

Manganese,  if  present  in  appreciable  quantity, 
is  separated  before  the  precipitation  of  the  cal- 
cium, as  follows:  The  filtrate  from  the  iron  pre- 
cipitate is  slightly  acidulated  with  hydrochloric 
acid,  concentrated,  and  the  manganese  precipi- 
tated as  sulfid  by  colorless  or  slightly  yellow  solti- 
tion  of  ammonium  sulfid.  The  flask,  which 
should  be  nearly  full,  is  stoppered,  allowed  to  rest 
in  a  moderately  warm  place  until  the  precipitate 
has  thoroughly  settled,  filtered,  washed  with 


GENERAL  QUANTITATIVE    ANALYSIS.  67 

dilute  ammonium  sulfid  water,  and  purified  by 
dissolving  in  a  small  quantity  of  hydrochloric 
acid  and  reprecipitating  with  ammonium  sulfid. 
It  is  filtered  off,  washed  as  before,  dried,  placed  in 
a  weighed  porcelain  crucible,  covered  with  a  little 
sulfur,  and  ignited  in  a  current  of  hydrogen  intro- 
duced into  the  crucible  by  a  tube  passing  through 
a  hole  in  the  cover.  The  pure  manganese  sulfid 
thus  obtained  is  allowed  to  cool  and  weighed. 
The  weight  multiplied  by  0.633  gives  manganese. 

Sulfates. — 500  c.c.  of  the  clear  water  are 
slightly  acidulated  with  hydrochloric  acid,  heated 
to  boiling,  and  barium  chlorid  solution  added  in 
moderate  excess.  The  precipitated  barium  sulf  ate 
is  allowed  to  subside  completely,  collected  upon  a 
filter,  washed  thoroughly,  dried,  and  incinerated. 
The  weight  multiplied  by  0.411  gives  SO*.  If 
the  proportion  is  very  low,  it  will  be  advisable 
to  concentrate  the  water  to  much  smaller  bulk 
before  precipitating. 

Control.  Potassium,  Sodium,  and  Lithium. — 
From  250  to  1000  c.c.  of  the  water,  according  to 
the  amount  of  solid  matters  present,  are  evapo- 
rated to  dryness  in  a  platinum  dish,  and  the  resi- 
due treated  with  a  small  amount  of  water  and 
sufficient  dilute  sulfuric  acid  to  decompose  the 
salts  present.  The  dish  should  then  be  covered 
and  placed  upon  the  water-bath  for  ten  minutes, 
after  which  any  liquid  spurted  on  the  cover  is 


68  ANALYTIC    OPERATIONS. 

washed  into  the  dish,  the  whole  evaporated  to 
dry  ness  and  heated  to  redness.  A  few  drops  of 
ammonium  carbonate  solution  should  then  be 
mixed  with  the  residue,  and  the  ignition  repeated 
to  insure  the  removal  of  the  last  portions  of  free 
acid.  In  the  majority  of  cases  the  only  basylous 
elements  present  in  considerable  quantity  are 
calcium,  magnesium,  and  sodium.  The  sodium 
may  be  determined  indirectly,  therefore,  by  cal- 
culating from  the  amount  of  calcium  and  magne- 
sium found,  the  calcium  and  magnesium  sulfate 
in  the  residue,  and  subtracting  this  sum,  together 
with  the  silica,  from  the  total  residue. 

For  the  determination  of  potassium  and  so- 
dium in  ordinary  well  and  river  waters,  not  less 
than  2  liters  should  be  employed.  When 
lithium  is  to  be  determined,  it  is  generally  neces- 
sary to  use  much  more.  In  any  case,  as  the  alka- 
lies are  to  be  weighed  as  chlorids,  it  is  advisable, 
if  notable  amounts  of  sulfates  are  present,  to 
precipitate  them  by  addition  of  barium  chlorid. 

The  water  is  evaporated  to  about  200  c.c.,  a 
slight  excess  of  calcium  hydroxid  added  to  the  hot 
liquid — generally  3  c.c.  of  thin  milk  of  lime  will  be 
sufficient — and  the  heat  continued  for  several 
minutes.  It  is  then  washed  into  a  25o-c.c.  flask, 
disregarding  the  insoluble  portion  adhering  to 
the  dish,  which,  however,  should  be  thoroughly 
washed,  and  the  washings  added  to  the  flask. 


GENERAL  QUANTITATIVE    ANALYSIS.  69 

After  cooling,  the  flask  is  filled  up  to  the  mark 
with  distilled  water,  thoroughly  mixed,  the  pre- 
cipitate allowed  to  settle,  and  the  liquid  filtered 
through  a  dry  filter.  200  c.c.  of  the  filtrate 
are  measured  into  another  250  c.c.  flask,  ammo- 
nium carbonate  and  ammonium  oxalate  added, 
filled  with  water  up  to  the  mark,  mixed,  allowed 
to  settle,  filtered  through  a  dry  filter,  200  c.c.  of 
the  filtrate  measured  off,  and  evaporated  to 
thorough  dryness  in  a  platinum  crucible,  heating 
very  cautiously  at  the  last  stages,  to  avoid  loss 
by  spurting.  The  low- temperature  burner  is 
suited  for  this  purpose.  The  crucible  is  now 
covered  and  cautiously  heated  to  dull  redness, 
cooled,  and  weighed.  The  residue  contains  the 
potassium,  lithium,  and  sodium  as  chlorids. 
It  contains,  sometimes,  also,  traces  of  magnesium, 
which  may  be  removed  by  treating  again  with 
lime  and  ammonium  carbonate  and  oxalate.  It 
is  frequently  of  advantage,  in  evaporating  these 
saline  solutions,  to  add,  when  the  solution  be- 
comes concentrated,  several  c.c.  of  strong  hydro- 
chloric acid.  This  precipitates  the  greater  por- 
tion of  the  salts  in  a  finely  granular  condition, 
and  renders  loss  by  spurting  less  liable  to 
occur. 

If  potassium  and  sodium  chlorids  only  are 
present,  the  residue  is  dissolved  in  a  small 
quantity  of  water,  an  excess  of  a  concentrated 


70  ANALYTIC    OPERATIONS. 

neutral  solution  of  platinum  chlorid  added, 
evaporated  to  small  bulk  at  a  low  heat  on  the 
water-bath,  some  80  per  cent,  alcohol  added,  al- 
lowed to  stand,  the  clear  liquid  decanted  off  on 
a  small  filter,  and  the  residue  washed  in  this  way 
several  times  by  fresh,  small  portions  of  the  alco- 
hol. The  precipitate  is  then  washed  on  to  the 
filter  with  alcohol,  washed  again  with  the  alco- 
hol, thoroughly  dried  and  transferred  as  far  as 
possible  to  a  watch-glass.  The  small  portion  on 
the  filter  is  dissolved  off  and  the  solution  placed 
in  a  weighed  platinum  dish  and  evaporated  to 
dryness.  The  main  portion  on  the  watch-glass 
is  then  added,  and  the  whole  dried  to  a  constant 
weight  at  about  125°,  cooled,  and  weighed.  The 
weight  thus  found  multiplied  by  0.3  gives  the 
weight  of  potassium  chlorid.  This  subtracted 
from  the  combined  weight  of  the  chlorids  gives 
the  weight  of  sodium  chlorid. 

Lithium,  if  present,  is  best  separated  before 
the  treatment  with  platinum  chlorid.  The  fol- 
lowing method,  devised  by  Gooch,  gives  good 
results:  To  the  concentrated  solution  of  the 
weighed  chlorids,  amyl  alcohol  is  added  and 
heat  applied,  gently  at  first,  to  avoid  bumping, 
until  the  water  disappears  from  the  solution  and 
the  point  of  ebullition  becomes  constant  at  a 
temperature  which  is  approximately  that  at 
which  the  alcohol  boils  (132°),  the  potassium 


GENERAL   QUANTITATIVE    ANALYSIS.  71 

and  sodium  chlorids  are  deposited,  and  the  lith- 
ium chlorid  is  dehydrated  and  taken  into  solu- 
tion. The  liquid  is  then  cooled,  and  a  drop  or 
two  of  strong  hydrochloric  acid  added  to  recon- 
vert traces  of  lithium  hydroxid  in  the  deposit 
and  the  boiling  continued  until  the  alcohol  is 
again  free  from  water.  If  the  amount  of  lithium 
chlorid  be  small,  it  will  be  found  in  the  solution 
and  the  potassium  chlorid  and  sodium  chlorid 
in  the  residue,  excepting  traces  which  can  be 
allowed  for.  If  the  lithium  chlorid  exceed  10  or 
20  milligrams,  the  liquid  may  be  decanted, 
the  residue  washed  with  amyl  alcohol,  dis- 
solved in  a  few  drops  of  water,  and  treated  as 
before.  For  washing,  amyl  alcohol,  previously 
dehydrated  by  boiling,  is  to  be  used  and  the 
filtrates  are  to  be  measured  apart  from  the  wash- 
ings. In  filtering,  the  Gooch  filter  with  asbestos 
felt  may  be  used  with  advantage,  applying 
gentle  pressure  by  the  aid  of  the  filter-pump. 
The  crucible  and  residue  are  ready  for  weighing 
after  gentle  heating  over  the  low-temperature 
burner.  The  weight  of  the  insoluble  chlorids  is 
to  be  corrected  by  adding  0.00041  for  every 
10  c.c.  of  amyl  alcohol  in  the  filtrate,  exclusive 
of  the  washings,  if  only  sodium  chlorid  be,  pres- 
ent; 0.00051  for  every  10  c.c.  in  only  potassium 
chlorid,  and  0.00092  in  the  presence  of  both  these 
chlorids. 


72  ANALYTIC    OPERATIONS. 

The  filtrate  and  washings  are  evaporated  to 
dryness  in  a  platinum  crucible  heated  with 
sulfuric  acid,  the  excess  driven  off,  and  the  res- 
idue ignited  to  fusion,  cooled,  and  weighed. 
From  the  weight  is  to  be  subtracted,  for  each 
10  c.c.  of  filtrate,  0.0005,  0.00059,  or  0.00109, 
according  as  only  sodium  chlorid,  potassium 
chlorid,  or  both  were  present  in  the  original 
mixture. 

Hydrogen  Sulphid. — The  following  is  the  proc- 
ess recommended  by  the  APHA. 

Standard  lodin  Solution. — 1.269  grams  of  pure 
dry  iodin  and  1.8  grams  of  pure  potassium  iodid 
are  dissolved  in  about  50  c.c.  of  water  and  the 
solution  made  to  1000  c.c.  It  is  N/ioo. 

Standard  Thiosulfate  Solution. — 2.5  grams  of 
pure  sodium  thiosulfate  are  dissolved  in  water 
and  made  up  to  1000  c.c.  This  is  approximately 
N/ioo  and  its  relation  to  the  iodin  solution  should 
be  ascertained  frequently,  as  it  does  not  keep 
well  even  in  the  dark. 

Starch  Solution. — See  p.  44. 

10  c.c.  of  the  iodin  solution  are  placed  in  a  dry 
1000  c.c.  flask,  1000  c.c.  of  the  sample  added,  the 
flask  well  closed,  shaken  and  allowed  to  stand  for 
several  hours.  The  excess  of  iodin  is  determined 
as  usual  by  titrating  with  thiosulfate  and  starch. 
i  c.c.  of  iodin  solution  is  equivalent  to  0.00017 
hydrogen  sulfid. 


GENERAL   QUANTITATIVE    ANALYSIS.  73 

Free  and  Half -bound  Carbonic  Acid. — Several 
methods  for  the  determination  of  these  data  have 
been  devised.  Pettenkofer's  is  much  used  but 
Forbes  and  Pratt,  after  careful  study  of  different 
methods,  favor  the  Lunge-Trillich  (also  termed  the 
Seyler)  method,  which  they  describe  as  follows : 

100  c.c.  of  the  sample  are  placed  in  a  tall  glass 
cylinder,  by  means  of  a  siphon  (in  order  to  avoid 
contact  with  air),  6  drops  of  neutral  alcoholic  solu- 
tion of  phenolphthalein  added,  and  N/so  sodium 
carbonate  run  in  from  a  buret  with  careful  stir- 
ring, until  a  faint  permanent  pink  is  obtained. 
If  the  water  contains  much  free  carbonic  acid, 
it  is  better  to  take  less  than  100  c.c.,  and  in  every 
case  care  must  be  taken  not  to  stir  the  sample  so 
vigorously  as  to  cause  loss  of  the  acid,  nor  to 
proceed  so  slowly  that  it  may  be  absorbed  from 
the  air.  The  solutions  must  be  carefully  standard- 
ized and  preserved  so  that  they  do  not  absorb 
the  acid.  The  fixed  carbonic  acid  is  determined 
on  another  portion  of  the  sample  by  Hehner's 
method  as  given  on  p.  48.  In  waters  acid  to 
phenolphthalein  this  will  be  equal  to  the  half- 
bound. 

When  the  water  is  alkaline  to  phenolphthalein, 
the  alkalinity  with  this  indicator  is  first  deter- 
mined, then  the  total  alkalinity  by  Hehner's 
method.  Twice  the  phenolphthalein  alkalinity 
subtracted  from  the  total  alkalinity  gives  the 


74  ANALYTIC    OPERATIONS. 

half-bound  acid,  no  free  acid  being  present  in 
this  case,  and  the  half -bound  being  less  than  the 
fixed.  If  the  water  is  neutral  to  phenolphthalein, 
the  half -bound  may  be  equal  to  the  fixed. 

Forbes  and  Pratt  have  modified  the  Petten- 
kofer  methods  as  follows : 

A  glass-stoppered  bottle,  holding  approxi- 
mately 480  c.c.,  is  accurately  calibrated  by  weigh- 
ing completely  filled  with  water.  It  is  filled  with 
the  water  to  be  analyzed  by  means  of  a  siphon, 
the  glass  stopper  inserted,  leaving  no  air-bubble, 
and  the  neck  of  the  bottle  wiped  dry.  The  glass 
stopper  is  then  carefully  removed,  and  the  57  c.c. 
of  the  water  withdrawn  by  means  of  an  accurately 
calibrated  pipet,  in  order  to  make  room  for  the 
reagents.  3  c.c.  of  barium  chlorid  solution  (8 
grams  per  1000  c.c.),  2  c.c.  of  saturated  am- 
monium chlorid  solution,  and  50  c.c.  of  standard 
barium  hydroxid  are  then  introduced,  the  bottle 
quickly  stoppered,  well  shaken,  and  set  aside  to 
settle. 

There  is  now  in  the  bottle  an  air  space  of  only 
2  c.c.,  which  is  left  to  avoid  the  possibility  of  loss 
of  liquid  when  the  stopper  is  inserted.  After 
the  precipitated  carbonates  have  completely 
settled,  several  portions  of  100  c.c.  are  siphoned 
off  and  titrated  with  N/so  sulfuric  acid,  against 
which  the  barium  hydroxid  is  standardized. 
Leffmann  and  Beam  used  barium  hydroxid 


ANALYSIS    OF   BOILER    SCALE.  75 

approximately  N/is,  preserved  out  of  contact  with 
the  air,  the  bottle  being  fitted  with  an  arrange- 
ment whereby  the  air  was  drawn  through  soda- 
lime  before  entering  either  the  bottle  or  the  buret. 
The  figure  obtained  by  averaging  several  results 
of  titration  of  portions  of  100  c.c.  is  taken  as  the 
true  value. 

The  use  of  this  large  quantity  of  water  and 
the  titration  of  100  c.c.  portions  reduce  consider- 
ably the  errors  due  to  the  difficulty  of  obtaining 
the  exact  end-point,  and  those  due  to  inaccuracies 
of  measurement. 

Boric  Acid.— To  detect  this  add  to  a  considerable 
volume  of  the  water  sufficient  sodium  carbonate  to 
render  it  distinctly  alkaline ;  evaporate  to  dryness, 
acidify  with  hydrochloric  acid,  moisten  a  slip  of 
turmeric  paper  with  the  liquid,  and  dry  it  at  a 
moderate  heat.  In  the  presence  of  boric  acid 
the  paper  will  assume  a  distinct  brown-red. 

ANALYSIS  OF  BOILER  SCALE. 

If  the  scale  is  made  up  of  pieces  of  decidedly 
different  quality,  some  being  hard  and  gritty, 
others  soft  and  friable,  separate  tests  should  be 
made  on  representative  samples  of  each  sort; 
but  if  the  general  character  is  fairly  uniform,  it 
will  be  sufficient  to  sample  the  entire  mass  and 
reduce  about  5  grams  to  a  fine  powder,  finishing 


76  ANALYTIC    OPERATIONS. 

in  an  agate  mortar.  All  of  the  quantity  selected 
as  the  sample  should  be  equally  finely  powdered. 
0.5  gram  should  be  heated  in  a  covered  beaker 
with  moderately  strong  hydrochloric  acid,  until 
all  soluble  matter  is  dissolved ;  the  liquid  is  then 
evaporated  to  dryness  on  the  water-bath,  re- 
dissolved  in  water  containing  some  hydrochloric 
acid,  and  filtered.  The  precipitate  is  silica.  The 
filtrate  and  washings  are  mixed  and  divided  into 
convenient  parts.  One  part  is  used  for  the  de- 
termination of  sulfates,  and  the  other  for  iron 
oxid,  alumina,  calcium,  and  magnesium,  accord- 
ing to  the  methods  given  on  pages  64  to  66. 
Scale  often  contains  an  appreciable  amount  of 
oil.  This  may  be  determined  by  extracting  a 
known  weight  of  the  finely  powdered  material 
with  a  petroleum  spirit  that  leaves  no  residue  on 
evaporation  on  the  water-bath. 

SPECTROSCOPIC  EXAMINATION. 

For  the  ordinary  spectroscopic  examination  of 
a  water  a  simple  apparatus  will  suffice.  The 
arrangement  shown  in  the  cut  (Fig.  5)  is  a  small 
direct- vision  spectroscope,  held  in  a  universal 
stand,  with  an  adjustable  burner  as  the  source  of 
heat. 

For  the  examination  a  considerable  volume 
should  be  evaporated  nearly  to  dryness,  a  little 
hydrochloric  acid  being  added  near  the  end  of  the 


SPECTROSCOPIC   EXAMINATION. 


77 


process,  the  residue  placed  in  a  narrow  strip  of 
platinum  foil,  having  the  sides  bent  so  as  to  retain 
the  liquid,  and  heated  in  the  flame.  While  this 
method  will  be  sufficient  in  many  cases,  a  far 
better  plan  is  to  sepa- 
rate the  substance  sought 
for  in  a  state  of  approxi- 
mate purity  and  then  ex- 
amine with  the  spectro- 
scope.  Very  small 
traces  of  lithium,  for  in- 
stance, may  be  detected 
as  follows:  To  about 
1000  c.c.  of  the  water 
sufficient  sodium  carbon- 
ate is  added  to  precip- 
itate all  the  calcium 
and  magnesium,  and  the 
liquid  boiled  down  to 
about  one-tenth  its  bulk ; 
it  is  then  filtered,  the  fil- 
trate rendered  slightly 
acid  with  hydrochloric 
acid,  and  evaporated  to 
dryness.  The  residue  is  boiled  with  a  little  al- 
cohol, which  will  dissolve  out  the  lithium  chlorid. 
The  alcoholic  solution  is  evaporated  to  dryness, 
the  residue  taken  up  with  a  little  water  and 
tested  in  the  flame. 


FIG.  5. 


78  ANALYTIC    OPERATIONS. 

In  order  to  identify  with  certainty  any  line 
which  may  be  obtained,  it  is  only  necessary  to 
hold  in  the  flame  at  the  same  time  a  wire  which 
has  been  dipped  in  a  solution  of  the  substance 
supposed  to  be  present  and  to  note  whether  the 
lines  produced  by  it  and  the  material  under 
examination  are  identical. 

SPECIFIC  GRAVITY. 

In  the  great  majority  of  cases  the  determination 
of  specific  gravity  is  not  essential.  Ordinary 
river,  spring,  and  well  waters  contain  such  small 
proportions  of  solid  matter  that  it  is  usually  the 
practice  to  take  a  measured  volume  and  to  as- 
sume its  weight  to  be  that  of  an  equal  bulk  of 
pure  water.  If  the  proportion  of  solids  is  high, 
a  determination  of  the  specific  gravity  may  be 
desirable.  For  this  purpose  the  specific-gravity 
bottle  may  be  used.  This  consists  merely  of  a 
small  flask  provided  with  a  finely  perforated 
glass  stopper.  The  bottle  is  weighed  first  alone, 
then  filled  with  distilled  water  at  15.5°,  and  finally 
with  the  water  under  examination  at  the  same 
temperature.  In  filling  the  bottle,  the  liquid  is 
first  brought  to  the  proper  temperature,  the  bottle 
completely  filled,  the  stopper  inserted,  and  the 
excess  of  water  forced  out  through  the  perforation 
and  around  the  sides  of  the  stopper  carefully 


ACTION    OF    WATER    ON   METALS.  79 

removed  by  bibulous  paper.  The  weight  of  the 
water  examined  divided  by  the  weight  of  the 
equal  bulk  of  distilled  water  at  the  same  tem- 
perature gives  the  specific  gravity. 

Another  method,  and  one  which  gives  very 
satisfactory  results,  is  by  the  use  of  a  plummet. 
This  may  conveniently  consist  of  a  piece  of  a 
thick  glass  rod  of  about  10  c.c.  in  bulk,  or  of  a 
test-tube  weighted  with  mercury  and  the  open 
end  sealed  in  the  flame.  The  plummet  is  sus- 
pended to  the  hook  of  the  balance  by  means  of 
a  fine  platinum  wire  and  its  weight  ascertained. 
It  is  then  immersed  in  distilled  water  at  15.5°, 
and  the  loss  in  weight  noted.  The  figure  so 
obtained  is  the  weight  of  a  bulk  of  water  equal 
to  that  of  the  plummet.  This  having  been  de- 
termined, the  specific  gravity  of  any  water  may 
be  found  by  immersing  in  it  the  plummet  and 
noting  the  loss  in  weight.  This,  divided  by  the 
loss  suffered  in  pure  water,  gives  the  specific 
gravity. 

ACTION  OF  WATER  ON  METALS. 

The  most  important  are  actions  on  lead  and 
iron.  The  phenomena  have  been  extensively 
studied,  but  much  remains  to  be  determined.  It 
may  be  said,  as  a  general  principle,  that  oxygen 
and  carbonic  acid  in  solution  have  a  great  influ- 


8o  ANALYTIC    OPERATIONS. 

ence  in  determining  corrosion,  but  there  seems 
to  be  no  doubt  that  with  most  waters  minute 
amounts  of  common  metals  pass  into  a  colloidal 
state,  and  are  then  oxidized  or  transformed  into 
various  salts.  Whether  the  metal  will  remain 
in  the  dissolved  or  colloidal  condition  depends, 
therefore,  on  the  salts  present. 

Action  of  water  on  lead  has  great  sanitary  signi- 
ficance, as  even  in  minute  amounts  lead  will  soon 
produce  serious  toxic  effects.  The  action  on  iron 
is  chiefly  important  from  an  industrial  point  of 
view. 

It  will  not  be  necessary  to  give  at  length  the 
results  of  the  many  investigators — results  by  no 
means  always  concordant — but  the  following  are 
summaries  of  some  of  the  observations :  Crookes, 
Odling  and  Tidy  found  that  when  soft  waters 
did  not  act  on  lead  silica  was  present  in  notable 
amount,  while  with  waters  having  marked  action 
silica  was  in  small  amount.  These  results  were 
confirmed  by  laboratory  experiments.  They  also 
found  that  an  effective  way  of  silicating  a  water 
is  to  pass  it  over  a  mixture  of  flint  and  limestone. 
The  reason  for  this  was  pointed  out  later  by 
Carnelly  and  Frew,  who  showed  that  while  cal- 
cium carbonate  and  silica  both  exert  a  protective 
influence,  calcium  silicate  is  more  effective  than 
either;  and,  further,  that  in  almost  all  cases  in 
which  corrosion  takes  place,  it  is  greater  in  the 


ACTION    OF    WATER    ON   METALS.  8 1 

presence  of  oxygen.  This  is  particularly  the 
case  with  potassium  and  ammonium  nitrates  and 
with  calcium  hydroxid.  The  reverse  is  true  of 
calcium  sulfate,  which  is  more  corrosive  when  air 
is  excluded.  Their  experiments  also  show  that 
the  presence  of  calcium  carbonate  or  calcium 
silicate  altogether  prevents  corrosion  by  potas- 
sium and  ammonium  nitrates. 

As  the  result  of  an  elaborate  series  of  experi- 
ments, Muller  concludes  that,  while  chlorids, 
nitrates,  and  sulfates  all  act  upon  lead  pipes,  no 
corrosion  takes  place  in  the  presence  of  sodium 
acid  carbonate,  and  that  calcium  carbonate,  by 
taking  up  carbonic  acid,  acts  in  the  same  way. 
This  latter  conclusion  is  at  variance  with  the  ob- 
servations of  Carnelly  and  Frew,  who  found  that 
calcium  carbonate  is  equally  effective  when 
carbonic  acid  is  excluded.  Muller  also  states 
that  surface  waters,  contaminated  by  sewage  and 
containing  large  amounts  of  ammoniacal  com- 
pounds, will  dissolve  lead  under  all  circumstances. 

Allen  has  shown  that  water  containing  free 
acid,  including  sulfuric  acid,  acts  energetically 
upon  lead.  This  is  not  surprising  in  view  of  the 
later  experiments,  which  prove  that  even  calcium 
sulfate  is  corrosive.  Later,  Carleton- Williams 
found  that  even  in  the  presence  of  free  acid,  cor- 
rosion may  be  prevented  by  the  addition  of 
sufficient  silica.  His  experiments  also  confirm 
6 


82  ANALYTIC    OPERATIONS. 

the  view  generally  held,  that  soluble  phosphates 
protect  lead  to  a  marked  degree. 

The  above  data  lead  to  the  following  classifi- 
cation : 

Corrosive:  Free  acid  or  alkalies,  oxygen,  ni- 
trates, particularly  potassium  and  ammonium 
nitrates,  chlorids,  and  sulfates. 

Non-corrosive  and  preventing  corrosion  by 
the  above:  Calcium  carbonate,  sodium  acid  car- 
bonate, ammonium  carbonate,  calcium'  silicate, 
silica,  and  soluble  phosphates. 

All  these  investigations  overlook  the  possibility 
of  the  initial  action  being  the  formation  of  col- 
loidal lead,  so  it  is  likely  that  later  experiments 
will  throw  more  light  on  the  question. 

As  regards  the  action  on  iron,  the  following 
data  are  taken  from  a  recent  report  by  Hale: 
Corrosion  is  rapid  in  new  pipe:  steel  is  most 
readily  attacked,  wrought  iron  next,  galvanized 
iron  the  least.  The  chief  agent  in  dissolving  iron 
and  holding  it  in  solution  is  carbonic  acid;  the 
chief  agent  in  rusting  is  oxygen.  By  the  action 
of  carbonic  acid  about  70  per  cent,  of  the  oxygen 
comes  from  the  decomposition  of  water,  hydrogen 
being  set  free;  the  remainder  is  derived  from  the 
dissolved  oxygen.  Soft  waters  containing  much 
carbonic  acid  are  most  corrosive;  hard  waters 
cause  but  little  complaint  as  a  rule  as  the  iron 
becomes  soon  coated. 


ACTION    OF    WATER    ON    METALS.  83 

The  action  in  distribution  services  probably 
never  reaches  completion  on  account  of  the  pro- 
tecting scale  of  oxid.  Since  in  distribution  there 
is  no  exhaustion  of  oxygen,  an  increase  of  carbonic 
acid  may  mean  an  increase  of  iron  in  the  water, 
and  this  would  be  precipitated  in  the  hot  water 
system. 

Neutralization  of  both  free  and  half-bound 
carbonic  acid  is  inadvisable  as  the  slightest 
excess  of  alkaline  hydroxid  will  increase  corrosion 
and,  in  hot  water,  increase  the  solution  of  zinc. 
It  is  also  stated  that  this  excess  will  interfere 
with  the  reaction  with  alum,  with  color  removal 
and  produce  deposits  that  choke  pipes  and 
meters.  Neutralization  of  free  carbonic  acid  is 
advisable. 

The  corrosive  action  of  water  very  poor  in 
solids  can  be  materially  diminished  by  filtration 
through  crude  bone-charcoal. 

In  boilers,  the  greatest  corrosion  is  generally 
observed  at  the  point  at  which  the  cold  water 
enters,  since  there  the  gases  are  driven  out  of 
solution  and  attack  the  metal. 

The  corrosive  action  of  oxygen  and  carbonic 
acid  in  waters  comparatively  pure,  such  as  those 
derived  from  mountain  springs,  was  repeatedly 
observed  by  Dr.  William  Beam,  in  examination  of 
waters  used  for  the  locomotives  of  the  Baltimore 
and  Ohio  Railroad.  The  waters  which  caused 


84  ANALYTIC    OPERATIONS. 

the  most  corrosion  were  mainly  those  contain- 
ing small  quantities  of  solid  matter,  the  full 
amount  of  oxygen,  and  considerable  carbonic 
acid,  but  no  other  acid  or  acid-forming  body. 

Free  acid,  other  than  carbonic  acid,  is  not 
often  found  in  water,  and  if  present  renders 
the  water  unfit  for  use,  unless  it  be  neutral- 
ized. Mine  waters  are  the  most  likely  to  contain 
free  acid,  sulfuric  acid  being  generally  present. 
Sometimes  the  acidity  is  due  to  organic  acids. 
These  act  very  injuriously  on  iron.  Allen  gives 
an  example  of  this  in  the  water  supplied  to  Shef- 
field, England,  which  he  found  to  contain  an 
organic  acid  in  amount  equivalent  to  from  3.5 
to  10  parts  of  sulfuric  acid  per  million. 

Boiler  Waters. — The  main  conditions  affecting 
the  value  of  a  water  for  steam-making  purposes 
are  its  tendency  to  cause  corrosion  and  the 
formation  of  scale. 

Magnesium  chlorid  may  be  harmful  if  in 
considerable  quantity.  At  a  temperature  of 
155°,  corresponding  to  an  effective  pressure  of 
four  atmospheres,  magnesium  chlorid  reacts 
with  water  to  form  magnesium  oxid  and  hydro- 
chloric acid,  the  latter  attacking  the  boiler,  es- 
pecially at  the  water-line.  If  at  the  same  time 
considerable  calcium  carbonate  is  present,  the 
action  may  be  somewhat  lessened,  but,  as  Allen 
has  pointed  out,  and  as  Leffmann  and  Beam 


ACTION    OF    WATER    ON    METALS.  85 

have  noticed,  there  may  still  be  corrosion,  so 
that  the  presence  of  more  than  a  small  quantity 
of  the  salt,  say  a  grain  or  two  to  the  gallon, 
may  be  considered  objectionable.  Allen  remarks 
that  the  presence  of  a  certain  amount  of  sodium 
chlorid  may  prevent  this  decomposition,  the 
two  chlorids  combining  to  form  a  stable  double 
salt.  The  addition,  therefore,  of  common  salt 
to  a  water  containing  magnesium  chlorid  may 
act  to  diminish  corrosion,  a  point  which  will 
bear  further  investigation. 

It  has  not  been  determined  how  far  the  presence 
of  nitrites,  nitrates,  and  ammonia  affects  the 
quality  of  water  for  steam-making  purposes;  but 
it  is  more  than  probable  that  they  act  harmfully, 
especially  the  nitrates,  which  are  frequently 
present  in  large  amount. 

Scale  is  composed  of  matters  deposited  from 
the  water  either  by  the  decompositions  induced 
by  the  heat  or  by  concentration.  When!' the 
deposit  is  loose,  it  is  termed  sludge  or  mud,  and 
usually  consists  of  calcium  carbonate,  magnesium 
oxid,  and  a  small  amount  of  magnesium  car- 
bonate. The  magnesium  oxid  is  formed  by  the 
decomposition  of  the  magnesium  carbonate  and 
chlorid. 

The  formation  of  sludge  is  the  least  objection- 
able effect,  since  it  may  readily  be  removed  by 
" blowing  off,"  provided  that  care  is  previously 


86  ANALYTIC    OPERATIONS. 

taken  to  allow  the  flues  to  cool  down  so  that 
when  the  water  is  removed  the  heat  of  the  flues 
may  not  bake  the  deposit  to  a  hard  mass. 
Waters  containing  calcium  sulfate  form  hard  in- 
crustations difficult  to  remove  and  causing  great 
loss  of  fuel  by  interfering  with  the  transmission 
of  the  heat  to  the  water.  It  not  only  forms  a 
hard  incrustation  in  itself,  but  becomes  in- 
corporated with  the  mud,  and  renders  it  also 
hard.  The  hard  scale  will  also  contain  practically 
all  the  silica  and  the  iron  and  aluminum  present 
in  the  water,  besides  any  matters  originally  held 
in  suspension. 

It  follows  from  the  above  that  a  water  only 
temporarily  hard  will,  if  care  is  taken  in  the 
management  of  the  boiler,  cause  the  formation 
merely  of  a  loose  deposit  of  sludge — temporary 
hardness  being  due  in  the  main  to  calcium  and 
magnesium  carbonates.  A  water  permanently 
hard  will  probably  form  a  hard  scale,  since 
such  hardness  is  usually  due  to  calcium  sulfate. 
For  methods  of  analyzing  scale,  see  page  75. 

In  accordance  with  these  principles,  the  analy- 
sis of  a  water  for  steam-making  purposes  may 
include  the  determinations  of  free  acid,  total 
solid  residue,  SO4,  Cl,  Ca,  Mg,  temporary  and 
permanent  (non-carbonate)  hardness.  In  cases 
in  which  the  qualitative  tests  show  but  small 
amounts  of  SO4  and  Cl,  the  analysis  may  be 


ACTION    OF    WATER    ON    METALS.  87 

limited  to  the  determinations  of  the  temporary 
and  permanent  hardness. 

In  the  laboratory  of  the  Pennsylvania  Railroad 
an  approximate  determination  of  scale-forming 
ingredients  is  made  in  the  following  manner: 
The  total  solids  obtained  by  evaporation  are 
treated  with  66  per  cent,  alcohol  and  the  undis- 
solved  residue  is  denominated  "scale-forming 
material." 

It  has  been  pointed  out  in  an  earlier  chapter 
that  it  is  not  possible  to  deduce  from  the  analytic 
results  the  exact  forms  in  which  the  various 
elements  are  combined,  but  since  it  is  known  that 
at  the  high  temperature  ordinarily  reached  in 
boilers  definite  chemical  changes  occur,  it  is 
safest  to  exhibit  the  maximum  amount  of  corro- 
sive and  scale-forming  ingredients  which  the 
water  under  these  circumstances  could  develop. 
Thus,  since  calcium  sulfate  is  practically  insoluble 
in  water  above  100°,  the  proportion  of  calcium 
sulfate  may  be  regarded  as  such  as  would  be 
formed  by  the  total  quantity  of  calcium  or  the 
total  quantity  of  SO4,  according  to  which  is 
present  in  the  larger  ratio.  Similarly,  as  the 
decomposition  of  magnesium  chlorid  is  induced 
by  the  high  temperature  of  the  boiler,  the  analytic 
statement  should  indicate  the  maximum  pro- 
portion of  this  compound  obtainable  from  the 
magnesium  and  chlorin  present.  These  rules 


88  ANALYTIC    OPERATIONS. 

can  not  apply  absolutely  to  waters  rich  in  alkali 
carbonates,  since  these  would  neutralize  any  acid 
formed  from  the  magnesium  chlorid,  or  even 
prevent  its  formation,  and  would  prevent,  to  a 
large  extent,  the  formation  of  calcium  sulfate. 
Much  remains  to  be  determined  concerning  the 
effects  of  the  high  temperature  and  concentration 
to  which  boiler  waters  are  subjected. 

General  Uses. — In  regard  to  the  quality  of 
water  for  other  than  steam-making  purposes, 
such  as  brewing,  dyeing,  tanning,  etc.,  no  detailed 
methods  or  standards  can  be  laid  down.  The 
nearest  approach  to  purity  that  can  be  secured 
in  the  supply  will  be  of  the  greatest  advantage. 
The  more  objectionable  qualities  will  be  large 
proportion  of  organic  matter,  especially  if  it  dis- 
tinctly colors  the  water,  excessive  hardness,  and 
notable  amounts  of  iron  or  free  mineral  acid.  It 
is  stated  that  i  part  of  iron  per  million  will 
render  water  unsuitable  for  bleaching  establish- 
ments. It  has  been  noted  that  a  large  propor- 
tion of  active  microbes  is  injurious  in  the  manu- 
facture of  indigo.  In  artificial  ice  making,  a 
very  pure  water  must  be  used  if  a  clear  and 
colorless  product  be  desired.  Any  suspended  or 
dissolved  coloring-matter  will  be  concentrated 
by  the  freezing  and  appear  in  the  bottom  or 
center  of  the  mass. 


BIOLOGIC   EXAMINATIONS.  89 

BIOLOGIC  EXAMINATIONS. 

In  a  comprehensive  sense  the  living  organisms 
of  water  include  representatives  of  all  the  great 
groups  of  animals  and  plants.  The  higher  forms 
are  absent  from  very  foul  water.  From  an 
analytic  point  of  view,  observation  is  limited  to 
the  determinations  of  those  forms  which  are  in- 
appreciable to  the  unassisted  eye.  So  far  as 
regards  some  of  the  moderately  complex  organ- 
isms, such  as  the  minute  crustaceans,  algse, 
desmids,  and  even  the  amebae,  it  may  be  said 
that  while  some  general  inferences  as  to  the 
character  and  history  of  the  water  may  be  de- 
duced from  an  identification  of  the  specific 
forms,  no  definite  sanitary  signification  can  be 
attached  to  them.  From  what  is  now  known 
of  the  life-history  of  many  parasitic  organisms, 
it  is  evident  that  water  that  is  freely  accessible 
to  any  animal  forms  is  liable  to  be  dangerously 
polluted.  Moreover,  the  dead  bodies  of  such 
animals  will  furnish  food  to  many  forms  of  mi- 
crobes and  thus  assist  in  the  multiplication  of  the 
latter.  The  ova  of  the  entozoa  might  in  some 
cases  be  detected  by  careful  search,  and  would 
indicate  recent  pollution  of  a  highly  dangerous 
character. 

The  number  of  the  higher  forms  present  in  any 
sample  will  depend  very  much  upon  the  point 


QO  ANALYTIC    OPERATIONS. 

at  which  it  is  collected,  they  being  more  numerous 
in  the  neighborhood  of  large  plants  and  at  the 
bottom  and  sides  of  streams. 

Several  observers,  notably  Sedg wick  and  Rafter, 
have  paid  considerable  attention  to  the  recogni- 
tion of  the  animal  and  vegetable  forms  in  surface 
waters.  Some  of  these  forms  cause  disagreeable 
odors  and  colors ;  in  the  warm  season  of  the  year, 
when  such  water  is  stored  in  reservoirs,  consider- 
able annoyance  is  felt  by  the  users,  and  the  engi- 
neer-in-charge  is  subjected  to  much  criticism. 
It  has  been  found  that  even  crude  filtration 
methods,  such  as  allowing  the  water  to  pass 
through  a  dike  of  porous  soil  before  storing  it  in 
a  reservoir,  will  diminish  the  tendency  to  these 
conditions.  Cleansing  a  reservoir,  disinfecting 
the  inner  surface,  for  instance,  by  whitewashing, 
has  also  improved  the  condition. 

Observation,  especially  in  Massachusetts,  has 
shown  that  reservoirs  intended  for  even  moder- 
ately prolonged  storage  of  water  should  be  clean 
— that  is,  organic  matter  of  any  kind  should  not 
be  allowed  to  accumulate  on  the  bottom  and 
sides.  Drown  states  that  while  the  water  in 
one  basin  became  foul  from  stagnation,  in 
another  which  was  carefully  prepared  by  the  re- 
moval f of  all  soil  and  vegetable  matter,  and  is 
supplied  by  a  brown,  swampy  water  from  a 


BIOLOGIC    EXAMINATIONS.  QI 

district  almost  entirely  free  from  pollution,  the 
water  is  good  at  a  depth  of  40  feet. 

In  Philadelphia,  large  storage  reservoirs  were 
used  for  water,  often  very  muddy,  but  little 
trouble  from  the  growth  of  microscopic  organisms 
occurred.  These  reservoirs  are  artificial  basins. 
They  are  now  mostly  used  for  filtered  water. 

Sedg wick's  method  of  collecting  organisms 
other  than  microbes,  with  some  modifications  by 
Williston,  is  as  follows : 

In  ordinary  cases  about  100  c.c.  are  employed. 
Sometimes  it  will  be  advantageous  to  use  double 
this  quantity,  at  other  times  much  less.  In  rare 
cases  the  examination  can  be  made  upon  un- 
filtered  water.  Originally  sand  was  employed 
for  a  filter  material,  but  Williston  finds  that  pre- 
cipitated silica,  made  by  decomposing  silicon 
fluorid  with  water,  is  more  satisfactory.  This  pre- 
cipitated silica  is  a  commercial  article,  and  its 
method  of  preparation  is  given  in  all  the  larger 
manuals  of  chemistry. 

A  small  glass  funnel  with  an  even-calibered 
stem  is  selected,  and  the  lower  end  of  the  stem 
plugged  with  a  little  absorbent  cotton,  upon  which 
a  layer  4  mm.  deep  of  the  filter-material  is  placed. 
The  water  is  passed,  the  pledget  of  cotton  re- 
moved, and  the  filter-material  washed  down  with 
filtered  or  distilled  water  into  a  cell  intended  for 
microscopic  examination.  This  cell  is  a  glass 


92  ANALYTIC    OPERATIONS. 

plate  accurately  ruled,  to  which  is  attached  a 
brass  cell  50  mm.  long  by  10  mm.  wide,  of  depth 
sufficient  to  hold  about  2  c.c.  of  water.  After 
the  material  has  been  allowed  to  distribute  itself 
and  settle  in  the  cell,  it  is  examined  with  a 
moderate  power,  and  the  different  organisms  in  a 


number  of  the  squares  counted.  Each  organism 
may  be  counted  by  itself,  if  occurring  in  large 
numbers,  the  average  of  a  few  squares  being 
sufficient  for  the  purpose.  Organisms  less  numer- 
ously represented  may  be  counted  by  averaging 
a  larger  number  of  squares.  Fig.  6,  cut  loaned 


BIOLOGIC    EXAMINATIONS.  93 

by  Arthur  H.  Thomas  Co.,  shows  a  more  elaborate 
form. 

Filtering  in  this  manner  can  not  be  relied  upon 
in  all  cases.  Indeed,  in  most  cases  the  unfiltered 
water  also  should  be  examined.  Some  of  the 
minute  unicellular  organisms  pass  readily  through 
the  small  extent  of  sand  or  precipitated  silica,  or 
even  through  filter-paper. 

It  is  not  unlikely  that  the  high-speed  cen- 
trifugal apparatus  now  used  in  laboratories, 
associated  with  the  employment  of  some  fine 
precipitant,  will  aid  in  these  investigations. 

Owing  to  the  great  differences  in  the  size  of 
microscopic  organisms,  the  mere  enumeration  of 
their  numbers  is  not  always  an  index  of  the 
amount  of  living  matter  in  suspension.  To  ob- 
viate this,  Whipple  has  suggested  a  standard 
unit  of  size,  estimating  by  means  of  it  the  total 
volume  of  the  organisms,  and  not  their  number. 
He  finds  by  this  method  that  the  analytic  and 
biologic  results  correspond  much  more  closely 
than  when  mere  numbers  are  recorded.  The 
unit  is  an  area  of  400  microns — that  is,  a  square 
of  20  microns  one  side.  The  results  are  stated 
in  number  of  standard  units  per  c.c. 

Whipple  has  investigated  the  conditions  in- 
fluencing the  growth  of  the  microscopic  organ- 
isms in  water.  He  finds  that  diatoms  thrive 
best  with  a  supply  of  nitrates  and  a  free  circula- 


94  ANALYTIC    OPERATIONS. 

tion  of  air;  temperature  alone  has  no  very  direct 
effect.  Infusoria  will  be  found  in  largest  numbers 
when  the  water  contains  the  greatest  amount  of 
finely  divided  organic  matter.  When  the  condi- 
tions bring  about  a  circulation  of  the  water,  the 
organisms  are  not  only  brought  constantly  in 
contact  with  new  food  materials,  but  are  en- 
abled to  reach  the  upper  layers  of  the  water  where 
oxygen  is  abundant. 

Bacteriologic  examinations  may  be  qualitative 
or  quantitative.  The  former  involves  the  deter- 
mination of  the  species  of  microbes  present,  es- 
pecially those  having  disease-producing  power, 
or  characteristic  of  some  form  of  pollution.  The 
processes  are  usually  laborious,  requiring  ex- 
tensive laboratory  facilities.  Quantitative  ex- 
amination— microbe-counting,  as  it  may  be  called 
— is  the  determination  of  the  number  of  microbes, 
or  microbe-colonies,  that  can  be  grown  from  a 
given  volume  of  water  under  specified  conditions. 
As  the  growth  of  living  organisms  is  influenced 
by  all  external  conditions,  results  are  not  com- 
parable, unless  strict  uniformity  of  method  has 
been  observed.  Neglect  of  this  fact  renders  a 
very  large  part  of  the  earlier  work  and  some  of 
the  present-day  work  of  little  statistical  value. 
Among  the  conditions  materially  affecting  the 
growth  of  microbes  are  temperature,  reaction  of 
the  culture-medium  to  different  indicators,  de- 


BIOLOGIC    EXAMINATIONS.  95 

gree  of  exposure  to  light  and  air,  and  duration  of 
cultivation.  The  composition  of  the  culture- 
medium  has  much  influence,  and  it  is  difficult  to 
control  this  exactly,  owing  to  the  irregularity  of 
quality  of  some  of  the  materials  used. 

In  the  routine  of  water- analysis,  bacteriologic 
examinations  are  chiefly  determination  of  the 
number  of  living  microbes  in  a  given  volume  and 
detection  of  certain  types.  For  the  former  pro- 
cedure— microbe- counting — media  solid  at  ordi- 
nary temperatures,  but  liquid  at  or  about  blood- 
heat,  are  employed,  gelatin  or  agar  being  used. 
Gelatin-jelly  melts  below  blood-heat  (37°)  but 
agar  does  not,  hence,  as  will  be  seen  by  the  formu- 
las given  below,  the  latter  is  almost  entirely  used. 
Apparatus  and  materials  for  bacteriologic  work  are 
now  obtainable  in  standard  form  from  dealers 
and  only  brief  notice  is  needed. 

The  following  constitute  the  equipment  for 
water-bacteriology : 

Open-steam  sterilizer. 

Autoclave. 

Hot-air  oven. 

Incubating  Oven  with  Thermostat. — Many  forms 
are  now  in  use,  some  heated  by  gas,  some  by 
electricity.  The  latter  type  has  been  brought  to 
a  high  degree  of  efficiency  in  regulation  of  tem- 
perature, which  is  very  important,  as  the  oven 


96  ANALYTIC    OPERATIONS. 

should  not  have  a  range  of  over  i°  in  operation 
at  a  given  temperature. 

Test-tubes. — About  12  cm.  long  and  1.5  cm. 
diameter. 

Petri  Dishes. — For  the  smaller  sizes,  earthen- 
ware covers  are  obtainable,  which  are  better  than 
glass,  as  they  absorb  the  water  given  off  from 
the  culture,  and  which  collecting  in  drops,  may 
fall  on  the  culture  and  produce  confusion.  In 
lack  of  earthenware  covers,  thick  white  blotting- 
paper  fitted  tightly  to  the  inside  of  the  glass  will 
be  of  service. 

In  the  early  editions  of  this  work,  Leffmann 
and  Beam  described  a  method  of  "bottle-culture" 
in  which  flat  rectangular  bottles  were  used.  The 
same  idea  is  exemplified  in  "Kolle's  flasks,"  flat 
glass  flasks  with  a  broad  flat  neck. 

Ferment-tubes. — The  standard  dimensions  are: 
closed  arm  about  15  cm.  long,  1.5  cm.  diameter; 
bulb  about  4  cm.  in  diameter,  it  being  intended 
that  the  bulb  shall  be  able  to  hold  all  the  liquid 
from  the  longer  arm. 

Wire  baskets  for  holding  test-tubes. 

Ordinary  laboratory  apparatus,  such  as  pipets, 
burets,  funnels,  beakers,  cotton-wad,  tinfoil  cut 
in  squares,  5  cm.  on  the  side.  A  double-boiler,  of 
which  the  inner  vessel  will  hold  about  2000  c.c., 
is  needed. 

Gelatin. — Some   bacteriologists   use   a   French 


BIOLOGIC   EXAMINATIONS.  97 

gelatin  (Coignet)  but  most  prefer  a  special  form 
sometimes  termed  " gold-label  gelatin"  manu- 
factured in  Germany.  Much  uncertainty,  how- 
ever, prevails  in  regard  to  the  source  and  quality 
of  the  gelatin  sold  to  bacteriologists,  and  it  will  be 
safest  to  purchase  from  some  trustworthy  dealer 
who  is  in  touch  with  the  manufacturers.  Good 
gelatins  of  American  manufacture  are  obtain- 
able, but  bacteriologists  do  not  use  them.  The 
term  "gold  label"  has  no  value  as  any  one  may 
use  such  a  label. 

Gelatin  and  agar  often  contain  notable  amounts 
of  moisture,  and  it  is  recommended  that  each 
should  be  assayed  by  drying  a  small,  known, 
weight  at  105°,  and  allowing  for  the  moisture 
thus  ascertained  in  weighing  out  portions  for 
media. 

Agar. — The  ordinary  article  termed  "  thread 
agar,"  is  satisfactory.  Powdered  agar  is  made 
in  Germany;  it  is  more  expensive,  but  dissolves 
more  quickly. 

Peptone. — Witte's  dry  peptone  is  generally 
recommended,  but  a  good  peptone  is  made  in  the 
United  States. 

Glucose. — The  grade  termed  "crystallized, 
pure;"  it  consists  mostly  of  dextrose. 

Meat-extract. — It  is  customary  to  recommend 
"Liebig's  extract,"  but  this  term  has  no  positive 
value  as  any  one  can  so  designate  his  product. 
7 


98  ANALYTIC    OPERATIONS. 

It  is  probably  intended  to  limit  the  choice  to  the 
product  of  the  Liebig  Extract  of  Meat  Co.,  of 
London,  but  there  is  no  reason  to  give  this  pref- 
erence over  the  American  extracts. 

Sodium  Chlorid. — A  good  quality  of  table-salt 
will  serve. 

Lactose. — This  should  be  of  high  purity,  es- 
pecially  free  from  protein   matters   and   other 
carbohydrates. 
Preparation  of  Culture -media : 

Broth  (Bouillon). — Broths  are  fluid  media,  the 
basis  of  ordinary  broth  being  the  soluble  portions 
of  raw  beef.  Some  operators  prefer  to  obtain 
this  by  macerating  meat  in  cold  water  for  a 
number  of  hours,  but  the  general  custom  is  now 
to  use  commercial  meat-extracts.  A  standard 
broth  is  made  as  follows : 

Meat-extract 3  grams 

Peptone 10  grams 

Sodium  chlorid 5  grams 

Water 900  c.c. 

The  ingredients  are  heated  in  a  double-boiler 
until  dissolved,  made  up  to  1000  c.c.  and  the 
reaction  ascertained  as  described  on  page  99. 
The  APHA  deprecates  the  use  of  meat-extract, 
but  nevertheless  has  substituted  it  for  meat- 
infusion  in  several  cases  without  giving  any 
reason  for  such  action. 


BIOLOGIC    EXAMINATIONS.  99 

Reaction  of  Culture-media. — Culture-media  are 
now  brought  to  a  standard  reaction,  expressed  in 
per  cent,  of  N/i  acid  or  alkali  required  to  make 
the  solution  neutral,  acid  media  being  marked  +  , 
and  alkaline  media  — .  The  reaction  used  by 
American  bacteriologists  is  +  i  per  cent,  that  is, 
100  c.c.  of  the  media  should  require  i  c.c.  of  N/i 
alkali  to  produce  neutrality.  Phenolphthalein 
(0.5  c.c.  to  100  c.c.  of  50 per  cent,  alcohol)  must  be 
used  as  the  indicator. 

Determination  is  as  follows:  5  c.c.  of  the 
medium  are  mixed  with  45  c.c.  of  water,  the  mix- 
ture boiled  briskly  for  one  minute,  i  c.c.  of  the 
indicator  solution  added  and  the  liquid  titrated, 
while  boiling,  with  N/2o  sodium  hydroxid  to  a 
faint  but  distinct  pink.  The  amount  of  alkali 
to  be  added  to  the  whole  volume  of  the  medium 
to  bring  the  acidity  down  to  +  i  per  cent,  can  be 
easily  calculated. 

If  it  is  desired  to  use  meat  as  the  basis  of 
broth,  500  grams  of  beef  as  free  as  possible  from 
bone,  gristle  and  fat,  should  be  finely  divided 
in  a  meat-chopper,  and  macerated  overnight  in 
about  500  c.c.  of  water  between  o°  and  10°. 
The  liquid  is  strained  through  cloth,  obtaining  as 
much  liquid  as  possible,  and  substituted  for  the 
meat  extract,  the  amount  of  meat  here  given  being 
adapted  to  make  1000  c.c.  of  medium.  The 
mixture,  before  taking  the  reaction,  must  be 


100  ANALYTIC    OPERATIONS. 

heated  in  the  open-steam  sterilizer  to  coagulate 
albumin,  and  then  filtered. 

Plain  broth  is  but  little  used ;  it  is  generally 
enriched  with  special  ingredients  as  given  below. 
In  many  of  these  special  forms  the  sodium  chlorid 
is  omitted. 

Culture-media  should  be  clear.  Filtration, 
often  difficult,  is  best  carried  out  in  a  hot- water 
funnel.  Filters  of  cotton- wool  or  cotton  cloth 
may  be  used. 

Fermentations. — Under  this  term  is  included  the 
action  of  microbes  producing  transformation  of 
carbohydrates  by  which  notable  amounts  of  gas 
and  acids  are  produced.  The  gas  is  recognized 
and  measured  by  performing  the  tests  in  ferment- 
tubes,  which  are  filled  with  the  nutritive  medium, 
generally  a  sensitized  broth. 

The  bulk  of  the  gas  is  carbon  dioxid  and  hy- 
drogen, but  other  gases  such  as  methane  may  be 
produced.  Attempts  to  differentiate  microbes 
by  determining  the  ratio  of  the  different  gases 
have  not  been  successful. 

Ferment-tubes  should  be  well  cleaned,  sterilized 
in  open-steam,  charged  with  the  sterilized  sensi- 
tized broth  in  such  manner  that  the  longer  arm 
of  the  tube  is  quite  filled,  while  the  level  of  the 
liquid  in  the  short  arm  is  such  as  to  permit 
the  introduction  of  the  material  to  be  cultivated 


BIOLOGIC   EXAMINATIONS.  loi 

and  allow  the  overflow  when  the  gas  begins  to 
collect  in  the  long  arm. 

Fermentations  are  usually  made  at  37°  for  not 
less  than  forty-eight  hours.  They  are  often 
applied  as  a  preliminary  cultivation,  inoculation 
being  made  from  the  ferment-tube  into  other 
media. 

Solid  Culture-media. — The  elaborate  methods 
on  page  102  are  given  by  the  APHA.  The  meat 
should  be  finely  divided  in  a  meat-chopper.  It 
is  evident  from  the  present-day  literature  that 
American  bacteriologists  are  using  meat-extracts 
largely  in  these  solid  media  instead  of  meat-in- 
fusion, 3  grams  of  a  good  commercial  extract 
being  used  for  1000  c.c.  of  medium.  It  is  not  clear 
what  object  is  served  by  the  several  adjustments 
of  reaction.  It  would  seem  that  an  adjustment 
when  ready  to  sterilize  will  suffice. 

Litmus-lactose-agar  is  prepared  in  the  same 
manner  as  nutrient  agar  with  the  exception  that 
i  per  cent,  of  lactose  and  a  small  amount  of 
azolitmin  are  added  just  before  sterilization. 
Kahlbaum's  azolitmin  is  preferred,  as  it  is  readily 
soluble  and  does  not  alter  the  reaction. 

Lactose-broth. — This  contains  i  per  cent,  of 
lactose.  A  sufficient  approximation  will  be  ob- 
tained by  adding  10  grams  of  lactose  to  1000  c.c. 
of  broth,  prepared  as  described  on  page  98.  It 


10'J  ANALYTIC    OPERATIONS. 

is  recommended  that  the  mixture  be  made  neu- 
tral to  phenolphthalein. 

GELATIN.  AGAR. 

1.  Boil  15  grams  agar  in  500  c.c. 

of  water  for  30  minutes,  or 
digest  for  15  minutes  in  an 
autoclave.  Make  up  the 
weight  to  500  grams  and 
allow  the  mixture  to  cool  to 
60°. 

2.  Macerate  500  grams  lean      Macerate    500    grams    lean 
meat  for  24  hours  in  1000          meat  in  500  c.c.  of  water  for 
c.c.  of  water  at  o°.  24  hours  at  o°. 

3.  Make  up  loss  by  evaporation. 

4.  Strain  liquid  through  cotton  cloth. 

5.  Weigh  filtrate. 

6.  Add  i%  of  peptone  and      Add  2%  of  peptone. 
10%  of  gelatin,  both  on 

dry  basis. 

7.  Warm   on  water-bath    (double -boiler)   with 
stirring  until  substances  are  dissolved,  at  not 
over  60°. 

8.  To  500  grams  of   the    meat 

solution  add  500  c.c.  of 
agar  solution  at  not  over 
60°. 

9.  Titrate  after  boiling  for  i  minute. 

10.  Adjust  reaction  to  +  i  %  by  adding  N/i  hy- 

drochloric acid  or  sodium  hydroxid  as 
required. 

n.  Heat  over  boiling  water  for  40  minutes. 

12.  Restore  loss  by  evaporation;  readjust  reac- 

13.  tion  to  + 1  %,  if  necessary,  boil  5  minutes  over 
free  flame. 

14.  Make  up  loss  by  evaporation. 

15.  Filter  through  absorbent  cotton  and  cotton  cloth, 
refiltering  until  clear. 

1 6.  Titrate  and  record  final  reaction. 

17.  Place  in  tubes  (10  c.c.  in  each). 

1 8.  Sterilize  15  minutes  in  autoclave  at  120°  or  in 
streaming  steam  for  30  minutes  on  three  suc- 
cessive days. 

19.  Put  tubes  promptly  in  ice-      Store  in  ice-chest  in  moist 
chest  in  moist  atmos-          atmosphere. 

phere. 


BIOLOGIC    EXAMINATIONS.  103 

Litmus-milk. — Fresh  milk  of  the  purest  attain- 
able quality  is  placed  over  night  in  the  ice- 
chest,  the  cream  removed  as  closely  as  possible, 
and  the  skimmed  milk  siphoned  from  any  sedi- 
ment. (It  would  seem  that  separator-skim  could 
be  substituted  without  detriment).  The  re- 
action must  be  +  i  per  cent,  i  per  cent,  of 
azolitmin  is  added  and  the  material  promptly 
tubed  and  sterilized. 

Lactose-bile. — Jackson,  who  has  worked  largely 
with  this  medium,  gives  data  for  its  prep- 
aration in  best  form.  Commercial  inspis- 
sated bile  is  not  very  satisfactory.  Fresh  ox- 
bile  filtered  and  sterilized  in  the  autoclave  for 
thirty  minutes  at  120°  will  keep  for  a  long  while. 
Bile  also  may  be  evaporated  to  dryness  at  a  low 
temperature  and  preserved  in  this  form.  On 
an  average  1000  c.c.  of  bile  will  yield  no 
grams  of  residue,  and  therefore,  n  grams  of  it 
will  suffice  for  100  c.c.  of  solution,  i  gram  of 
peptone  and  i  gram  of  lactose  are  added  to 
100  c.c.  of  bile  solution. 


Hesse-agar. — Agar  (dried  at 

105°  for  30  minutes),.  4.5  grams 

Peptone, 10 .  o 

Meat-extract, 5.0 

Sodium  chlorid, 8.5 

Water,  .  1000  c.c. 


104  ANALYTIC    OPERATIONS. 

The  agar  is  dissolved  in  500  c.c.  of  the  water; 
the  other  ingredients  are  dissolved  in  the  re- 
mainder, the  solutions  mixed,  boiled  for  thirty 
minutes,  cooled,  made  up  to  1000  c.c.,  and  fil- 
tered through  absorbent  cotton  held  in  the 
funnel  by  cotton  cloth.  The  liquid  should  be 
clear.  The  reaction  is  adjusted  to  -j-  i  per 
cent.  The  medium  is  sterilized  in  tubes  con- 
taining 10  c.c.  each  at  120°  for  twenty  min- 
utes, after  which  it  should  be  cooled  as  quickly  as 
possible  and  kept  in  a  cool,  moist  atmosphere. 

Endows  Medium. — This  is  enriched  with  de- 
colorized rosanilin,  under  such  conditions  that 
the  typhoid  bacillus  removes  the  decolorizing 
influence  and  the  colonies  appear  bright-red. 
The  APHA  formula  differs  measurably  from  that 
given  by  Endo,  being  based  on  a  formula  advised 
by  Kendall  and  Walker  and  used  by  them  for 
isolating  a  dysentery  microbe  from  intestinal 
discharges.  The  following  formula  is  substan- 
tially that  given  by  the  APHA,  except  some 
unnecessary  manipulations. 

Agar, 30  grams  (Endo  used  40  grams) 

Peptone, 10  grams 

Meat-extract,    5  grams     (Endo     used      beef- 
infusion) 

The  materials  are  heated  in  a  double-boiler 
with  about  1000  c.c.  of  water  until  dissolved, 


BIOLOGIC   EXAMINATIONS.  105 

sodium  carbonate  added  until  the  mass  is  neutral 
to  litmus  (azolitmin),  10  c.c.  of  a  10  per  cent, 
solution  of  sodium  carbonate  added,  the  liquid 
made  up  to  1000  c.c.,  charged  in  portions  of  100 
c.c.  into  150  c.c.  flasks  and  heated  for  two  hours 
in  open-steam. 

For  enriching,  the  following  solutions  are  used : 
Water  100  c.c.,  sodium  sulfite,  anhydrous,  i  gram. 
Alcohol  (95  per  cent.)  ico  c.c.,  basic  fuchsin,  i 
gram. 

The  sulfite  solution  must  be  fresh;  the  fuchsin 
solution  must  be  clear. 

Add  2  c.c.  of  the  fuchsin  solution  to  10  c.c. 
of  the  sulfite  solution,  steam  the  mixture  for 
a  few  minutes,  and  add  0.5  c.c.  of  it  i  gram 
of  lactose  to  each  100  c.c.  of  the  unsensitized 
base,  melt  in  open-steam,  pour  plates  and  allow 
to  cool  in  the  incubator.  The  solidified  mass 
should  be  clear.  Endo  inoculated  the  medium 
by  means  of  a  glass  rod  with  one  end  bent  at 
a  right  angle,  infecting  this  end  with  the  material 
to  be  cultivated  and  smearing  it  over  the  surface 
of  the  medium. 

Endo  medium  should  not  be  enriched  unless 
intended  for  prompt  use;  it  should  be  kept  in 
the  dark. 

Esculin  Medium. — This  is  a  special  medium 
devised  by  Harrison  and  Leek  for  recognition  of 
the  typhoid  bacillus. 


106  ANALYTIC    OPERATIONS. 

Esculin, o.i  gram 

Peptone, i .  o 

Sodium  taurocholate, o .  i 

Iron  citrate, 0.05     ' ' 

Water, 100 .  o      c.c. 

This  mixture  is  sterilized,  inoculated  (see 
page  1 08)  and  plated  in  the  usual  way.  It  should 
not  be  made  up  until  about  to  be  used.  The 
growth  of  the  typhoid  bacillus  causes  a  reaction 
between  the  esculin  and  iron  citrate  by  which 
black  spots  are  produced  at  points  at  which  the 
growth  is  taking  place. 

Indol  Reaction. — Indol,  C8H7N,  more  properly 
indin,  is  a  weak  base,  which  is  a  product  of  the 
growth  of  many  species  of  microbes,  and  the  de- 
tection of  it  may,  therefore,  be  utilized  as  a  dif- 
ferentiation test.  Kitasato  gives  the  following 
method  for  performing  the  test : 

10  c.c.  of  plain  broth  which  has  been  pre- 
viously inoculated  with  the  microbes  to  be  tested, 
and  kept  for  twenty-four  hours  at  37°,  are  treated 
with  i  c.c.  of  solution  of  pure  potassium  nitrite 
(0.02  gram  in  100  c.c.)  and  then  with  a  few  drops 
of  concentrated  sulfuric  acid.  In  the  presence  of 
indol  a  rose  or  deep  red  is  developed.  Bacillus 
coli  communis  gives  the  reaction  strongly;  B. 
typhosus  ordinarily  does  not  give  it. 


BIOLOGIC  EXAMINATIONS.  107 

CULTURE  PROCEDURES. 

Cultivation  in  gelatin  at  room  temperature 
usually  yields  a  larger  number  of  points  of 
microbic  life  than  in  agar  at  blood  heat,  due  to 
the  fact  that  many  microbes  do  not  grow  well  at 
the  higher  temperature. 

Culture-media  when  ready  for  use  are  usually 
distributed  in  test-tubes.  These  must  be  well 
cleaned.  In  laboratories  in  which  general  chem- 
ical work  is  also  carried  on,  the  mixture  of  crude 
chromic  and  sulfuric  acids  used  for  voltaic 
batteries  is  convenient  and  efficient,  the  tubes 
being  soaked  in  this  for  about  a  day  and  then 
thoroughly  rinsed.  Many  bacteriologists  use 
a  weak  solution  of  sodium  hydroxid.  The 
common  lye  sold  for  domestic  soap-making  is 
quite  satisfactory.  A  couple  of  grams  to  100  c.c. 
of  tap- water  will  serve.  The  tubes  are  boiled  in 
the  solution,  swabbed,  rinsed  and  allowed  to 
dry  in  an  inverted  position.  A  cotton  plug  is 
prepared  for  each  tube  care  being  taken  that  it  con- 
tains no  creases  and  does  not  fit  too  tightly.  The 
projecting  part  of  the  plug  is  clipped  moderately 
close  and  a  tinfoil  cap  placed  on  each.  The 
arrangement  is  sterilized  in  the  hot-air  oven  at 
150°  C.  When  cold,  the  tinfoil  and  plug  are 
carefully  removed,  10  c.c.  of  culture-medium 
put  into  each  tube,  with  as  little  outside  contami- 


108  ANALYTIC    OPERATIONS. 

nation  as  possible,  the  plug  and  cap  replaced, 
and  the  tubes  and  contents  sterilized  in  the 
open-steam  sterilizer.  Wire  baskets  are  used  to 
hold  the  tubes  during  the  sterilizations. 

For  making  cultures  definite  volumes  of  the 
water  sample  are  introduced  into  the  culture- 
medium,  and  if  this  is  a  solidifying  form,  it  is 
put  into  the  Petri  dish.  All  the  manipulations 
must  be  conducted  with  great  care  to  avoid 
contamination.  When  there  is  no  clue  to  the 
amount  of  microbes  present,  it  will  be  necessary 
to  make  cultures  with  different  proportions  of 
water.  Some  tubes  may  be  inoculated  with  a 
few  drops,  some  with  three  to  five  drops,  and  some 
with  i  c.c.  Some  operators  dilute  the  water 
considerably  and  take  small  measured  volumes. 
If  this  method  is  used,  the  diluting  water  must  be 
distilled  and  have  been  well  sterilized,  by  at 
least  five  minutes'  boiling,  and  cooled  out  of 
contact  of  air.  All  pipets,  dishes,  and  other 
apparatus  that  come  in  contact  with  the  water 
must  have  been  first  sterilized. 

The  test-tubes  containing  the  culture-medium 
are  warmed  gently,  just  enough  to  render  the 
culture-medium  fluid,  the  desired  volume  of  the 
water  added,  the  mixture  shaken  and  promptly 
poured  into  the  Petri  dishes,  covered  and  placed 
in  the  oven,  which  should  have  been  already 
raised  to  the  temperature  at  which  it  is  desired 


BIOLOGIC   EXAMINATIONS.  IOp 

to  conduct  the  work.  Unless  specially  desired 
otherwise,  cultures  should  be  made  in  the  dark. 
They  may  be  made  at  any  temperature  short  of 
that  at  which  the  medium  melts,  but  either 
ordinary  temperature  or  37°  is  usually  selected. 
The  condition  of  the  plates  should  be  observed  at 
intervals  of  twenty-four  hours,  and  the  points 
of  microbic  life  counted  and  recorded.  After 
some  days  the  growth  will  become  so  luxuriant 
or  the  liquefaction  of  the  medium  so  extensive 
that  accurate  observation  is  not  possible. 

Cultivation  in  flat  rectangular  bottles  or 
Kolle's  flasks  (page  96)  involves  simpler  manipula- 
tions and  less  risk  of  contamination,  especially 
with  molds,  which  are  serious  accidental  in- 
fections in  this  work.  Sufficient  of  the  medium 
is  put  into  each  bottle  or  flask  to  cover  the  flat 
surface  to  the  depth  of  a  few  mm.,  the  cotton 
plug  is  inserted  and  the  vessel  and  contents 
sterilized  as  usual,  that  is,  either  for  fifteen  minutes 
in  the  autoclave  at  120°,  or  for  twenty  minutes 
on  three  successive  days  in  the  open-steam  appa- 
ratus. The  medium  is  cooled  to  just  above  its 
melting  point,  the  proper  quantity  of  water  put 
in,  mixed  well,  the  bottle  or  flask  laid  on  the 
side  to  cool  and  then  incubated  at  the  proper 
temperature. 

If  the  microbic  points  are  numerous,  it  will  be 
necessary  to  employ  a  counting  scale.  For  the 


110  ANALYTIC    OPERATIONS. 

Petri  dish,  Pake's  modification  of  Lafar's  scale  is 
cheap  and  sufficient. 

General  Character  of  the  Microbes  in  Natural 
Waters. — The  microorganisms  of  natural  waters 
are  principally  included  in  the  genera  Bacillus 
and  Spirillum,  especially  the  former.  Micro- 
cocci  and  molds  are  rare,  and  are  generally  due 
to  contamination  by  dust. 

Microbes  are  also  differentiated  by  the  effects 
which  they  produce  upon  the  culture-medium. 
Some  species  rapidly  or  slowly  liquefy  the  jelly 
with  evolution  of  foul-smelling  gases;  others — 
chromogenic  microbes — produce  characteristic 
colors.  Many  do  not  produce  any  positive 
modification,  and  for  purposes  of  distinction  it 
is  usual  to  transfer  colonies  to  other  culture 
media.  Such  transfers  are  made  by  taking  up  a 
small  portion  of  the  culture  on  a  loop  of  wire 
that  has  just  been  sterilized  in  the  flame,  and 
introducing  this  into  the  culture-medium. 

Practical  Application  of  Bacteriologic  Methods. 
— As  noted  previously,  the  problems  presented  in 
the  commercial  or  works-laboratory  in  relation 
to  the  bacteriology  of  water  are  the  determination 
of  the  number  of  living  organisms  in  a  given 
volume  of  the  sample,  the  identification  and,  if 
possible,  isolation  of  specific  disease-producing 
forms.  Of  the  multitude  of  procedures  devised 
for  these  purposes,  a  few  only  deserve  special 


BIOLOGIC    EXAMINATIONS.  Ill 

mention.  These  are  cultivation  in  nutrient  agar 
(page  102)  at  37°,  for  microbe  counting,  in  broths 
enriched  with  carbohydrates  to  detect  fermenting 
(gas-producing  and  acid-producing  forms),  culti- 
vation in  milk  to  detect  coagulating  forms,  and 
in  bile-broths  for  further  differentiation,  espe- 
cially between  the  bacilli  of  the  colon  group  and 
the  true  germ  of  typhoid  fever. 

The  following  routine  for  the  examination  of 
water  supplied  by  corporations  engaged  in  inter- 
state commerce,  has  been  recently  issued  by  the 
U.  S.  Public  Health  Service,  and  may  be  regarded 
as  a  practical  series  of  procedures.  For  inter- 
pretation of  these  results  see  page  127. 

Cultivation  in  standard  agar  (page  102)  for 
twenty-four  hours  at  37°,  at  least  two  plates  being 
set. 

Cultivation  of  portions  of  10  c.c.  in  ferment- 
tubes  in  lactose-peptone-broth  (page  101)  at  37° 
for  forty-eight  hours,  not  less  than  five  tubes  being 
set. 

Cultivation  in  litmus-lactose-agar  (page  101) 
for  twenty-four  hours  at  37°. 

Inoculation  of  material  from  ferment-tubes  into 
Endo  medium  (page  104)  plates,  and  subsequent 
cultivation  of  typical  colonies  from  these  in- 
oculations in  ferment-tubes  containing  lactose- 
peptone-broth,  and  the  percentage  volume  of  gas 
noted. 


112  ANALYTIC    OPERATIONS. 

Jackson  has  worked  out  a  process  for  identifi- 
cation of  the  typhoid  bacillus  depending  on  the 
use  of  Hesse-agar. 

The  sample  is  cultivated  for  at  least  twenty-four 
hours  in  lactose  bile  (page  1 03 ) .  Eight  tubes  con- 
taining sterilized  distilled  water  are  arranged  in  a 
rack  with  eight  Petri  dishes,  each  set  being  desig- 
nated by  numbers  from  i  to  8.  In  tube  i  is  placed 
i  c.c.  of  the  culture,  the  contents  of  the  tube  are  well 
mixed,  i  c.c.  placed. in  dish  i,  and  i  c.c.  in  tube 
2.  The  contents  of  tube  2  are  mixed,  i  c.c.  put 
in  dish  2  and  i  c.c.  transferred  to  tube  3.  The 
dilution  is  carried  on  in  this  manner  until  the 
series  is  completed.  Each  dish  is  then  charged 
with  10  c.c.  Hesse-agar  (page  103)  which  has  been 
melted  and  cooled  to  40°,  the  content  of  each 
dish  is  well  mixed,  chilled  until  solid  and  incubated 
in  a  moist  atmosphere  at  37°  for  twenty-four 
hours. 

By  this  method  characteristic  growths  are  ob- 
tained from  the  typhoid  bacillus  but  only  when 
the  dilution  is  high  enough  to  give  but  few 
colonies  to  the  dish.  It  is  distinguished  from 
the  bacilli  of  the  colon  group  by  forming  colonies 
of  much  larger  size,  often  serveral  centimeters 
in  diameter,  showing  a  broad  translucent,  or 
scarcely  turbid,  zone  between  the  white  center 
and  the  narrow  white  border. 

Colonies  may  be  taken  off  for  identification  by 


BIOLOGIC    EXAMINATIONS. 


other  cultures  as  noted  on  page  104  or  for  micro- 
scopic examination. 

The  following  compositions  between  typical 
B.  coli  communis  and  B.  typhosus  are  given  by 
Abbott. 


CHARACTERISTICS. 

Motility, 

Growth  in  gelatin, . . 
Growth  in  milk,.. . . 


Growth  in  liquid 
media  containing 
glucose,  lactose, 
or  sucrose, 

Growth  in  solid 
media  containing 
lactose  and  lit- 
mus, . . 


Indol  reaction  in 
peptone  solution 
(48  hours  at  37°.) 


B.  TYPHOSUS. 

Conspicuous. 
Slow. 

No  coagulation; 
no  acidity. 


B.  COLI  COMMUNIS. 

Not  marked. 

Not  very  slow. 

Acidity  and  coagu- 
lations in  48 
hours  at  37°. 


No  evolution  of  gas.     Marked    evolution 
of  gas. 


Colonies  pale  blue ; 
no  reddening  of 
surrounding  me- 
dium. 


Rarely  present. 


Colonies  pink;  sur- 
rounding me- 
dium red. 


Always  present. 


INTERPRETATION  OF  RESULTS. 

STATEMENT  OF  ANALYSIS. 

The  composition  of  water  is  generally  expressed 
in  terms  of  a  unit  of  weight  in  a  definite  volume 
of  liquid,  but  much  difference  exists  as  to  the 
standard  used.  The  decimal  system  is  very 
largely  employed,  the  proportions  being  ex- 
pressed in  milligrams  per  1000  c.c.,  nominally 
parts  per  million;  or  in  centigrams  per  liter, 
nominally  parts  per  hundred  thousand.  The 
figures  are  often  given  in  grains  per  imperial 
gallon  of  70,000  grains,  or  the  U.  S.  gallon  of 
58,328  grains.  In  this  work  the  composition 
is  always  expressed  in  milligrams  per  1000  c.c. 
This  ratio  is  practically  equivalent  to  parts  per 
million,  except  in  case  of  water  very  rich  in 
solids,  1000  c.c.  of  which  will  weigh  notably 
more  than  one  million  milligrams.  Factors  for 
converting  the  different  ratios  are  given  at  the 
end  of  the  book. 

From  the  analysis  of  a  water  it  is  rarely  possible 
to  ascertain  the  exact  arrangement  of  the  ele- 
ments determined,  but  it  is  the  custom  to  assume 
arrangements  based  upon  the  rule  of  associating 
in  combination  elements  having  the  highest  af- 

114 


STATEMENT    OF    ANALYSIS.  115 

finities,  modifying  this  system  by  any  inferences 
derived  from  the  character  or  reactions  of  the 
water  itself.  It  is  preferable  to  express  the 
composition  of  a  water  by  the  proportion  of 
each  ion  present.  In  this  way  a  water  con- 
taining K2SO4  will  be  expressed  in  terms  of  K 
and  SO4,  respectively.  In  the  case  of  bodies 
like  CO2  and  SiO2,  which  may  possibly  exist 
free  in  the  water,  their  proportion  is  expressed 
as  such.  It  frequently  occurs  that  the  char- 
acteristics of  some  of  the  compounds  in  a 
water  are  sufficiently  marked  to  indicate  their 
presence,  and  there  can  be  no  objection  to 
suggesting,  in  connection  with  the  analytic  state- 
ment, the  inferences  which  may  thus  be  drawn. 

The  organic  matters,  or  derived  products,  are 
best  stated  in  terms  of  the  nitrogen  which  they 
contain,  thus  permitting  a  comparison  of  the 
different  stages  of  decomposition.  It  is  in- 
advisable to  represent  the  amount  of  unchanged 
organic  matter  in  terms  of  oxalic  acid,  as  has 
been  suggested,  or  to  express  the  nitrogen  in 
terms  of  albumin,  or  any  other  supposititious 
compound. 

The  results  of  bacteriologic  examinations 
should,  as  a  rule,  be  reported  as  "points  of 
microbic  life"  in  the  given  volume  of  water. 
Many  operators,  however,  report  the  number  of 
points  as  "colonies"  or  even  "bacteria." 


Il6       INTERPRETATION  OP  RESULTS. 

SANITARY  APPLICATIONS. 

Judgment  upon  the  analytic  results  from  a 
given  sample  of  water  depends  upon  the  class  to 
which  it  belongs,  and  to  the  particular  influences 
to  which  it  has  been  subjected.  A  proportion 
of  total  solids  which  would  be  suspicious  in  a 
rain  or  river  water,  would  be  without  signifi- 
cance in  that  from  an  artesian  well.  On  the 
other  hand,  a  subsoil  water  of  unobjectionable 
character  would  contain  a  proportion  of  nitrates 
which  would  be  inadmissible  in  the  case  of  a 
river  or  deep  water.  Location  has  also  much 
bearing  in  the  case;  subsoil  waters  near  the  sea 
will  be  found  to  contain,  without  invoking  sus- 
picion, proportions  of  chlorin  which  would  be 
ample  to  condemn  the  same  sample  if  derived 
from  a  point  far  inland.  Hence  the  importance 
of  recording,  at  the  time  of  collection,  all  ascer- 
tainable  information  as  to  the  surroundings  and 
probable  source  of  the  water. 

Analyses  of  surface  waters  have  little  value, 
unless  supplemented  by  a  careful  survey  of  the 
watershed  to  determine  sources  of  pollution. 
Such  survey  will  often  discover  conditions  suf- 
ficient to  condemn  the  supply,  even  though  the 
analyses  may  be  satisfactory.  Indeed,  it  may 
be  taken  as  a  fundamental  principle  that  surface 
water  from  even  a  sparsely  populated  district  will 
be  unsafe  for  use  unless  efficiently  filtered. 


SANITARY    APPLICATIONS.  117 

Color,  Odor,  and  Taste. — Water  of  the  high- 
est purity  will  be  clear,  colorless,  odorless,  and 
nearly  tasteless.  While  in  some  cases  a  de- 
cided departure  from  this  Standard  may  give  rise 
to  suspicion,  analytic  observations  are  necessary 
to  decide  the  point.  Water  highly  charged 
with  mineral  matters  will  possess  decided  taste, 
vegetable  matters  may  communicate  distinct 
color;  but,  on  the  other  hand,  it  may  be  highly 
contaminated  with  dangerous  substances  and 
give  no  indications  to  the  senses.  Well-waters 
occasionally  become  offensive  in  odor,  from 
penetration  of  tree  roots.  The  odor  often  recalls 
that  of  hydrogen  sulfid.  Sulfids  are,  indeed, 
often  formed  in  such  cases  by  the  abstraction 
of  oxygen  from  sulfates  under  the  influence 
of  microbes.  Such  waters  are  often  used  with- 
out apparent  injury,  but  it  is  probable  that 
if  direct  pollution  occurs,  the  danger  would 
be  enhanced  by  the  presence  of  the  vegetable 
matter. 

Surface  waters  collected  in  reservoirs  or  ponds 
often  become  very  offensive  from  the  growth  of 
algae,  but  apart  from  the  disgust  created  by  the 
water,  it  is  not  known  that  any  harmful  results 
occur  to  those  using  it. 

Turbidity  may  be  due  to  several  causes,  of 
different  degrees  of  danger,  but  is  always  ob- 
jectionable. 


Il8       INTERPRETATION  OF  RESULTS. 

Total  Solids. — Excessive  proportions  of  mineral 
solids,  especially  of  marked  physiologic  action, 
are  known  to  render  water  non-potable,  but  no 
absolute  maximum  or  minimum  can  be  assigned 
as  the  limit  of  safety.  Distilled  water  and 
waters  very  highly  charged  with  mineral  matter 
have  been  used  for  long  periods  without  ill 
effects.  The  popular  notion  that  the  so-called 
hard  waters  conduce  to  the  formation  of  urinary 
calculi  is  not  borne  out  by  clinical  experience  or 
statistical  inquiry.  Many  urinary  calculi  are 
composed  of  uric  acid,  and  are  the  results  of 
disorders  of  the  general  nutritive  functions. 

Sanitary  authorities  have  fixed  an  arbitrary 
limit  of  total  solids  of  about  600  parts  per 
million,  but  many  artesian  waters  in  constant 
use  exceed  this.  An  instance  is  found  in  the  well 
on  Black's  Island,  near  Philadelphia,  which  con- 
tains nearly  1200  parts  per  million,  is  very 
agreeable  in  taste,  and  has  been  in  constant 
use  for  some  years  by  a  number  of  persons 
without  injury.  The  assertion  that  water  to  be 
wholesome  must  contain  an  appreciable  pro- 
portion of  total  solids  is  also  not  demonstrated 
by  clinical  experience.  A  discussion  of  the  ef- 
fects of  special  mineral  ingredients — e.  g.,  mag- 
nesium sulfate,  ferrous  carbonate,  etc. — belongs 
to  general  therapeutics. 

The  odor  produced  on  heating  the  water  is 


SANITARY    APPLICATIONS.  Up 

often  of  much  use  in  detecting  contamination. 
Odors  similar  to  those  produced  by  heating  glue, 
hair,  rancid  fats,  urine,  or  other  animal  products, 
will  give  rise  to  grave  suspicion.  On  the  other 
hand,  a  more  favorable  judgment  may  be  given 
when  the  odor  recalls  those  given  off  in  the  heat- 
ing of  non-nitrogenous  vegetable  materials,  such 
as  wood-fiber. 

Poisonous  Metals. — The  proportion  of  iron  in 
water  constantly  used  for  drinking  purposes 
should  not  much  exceed  3  parts  per  million. 
Lead,  copper,  arsenic,  and  zinc  must  be  con- 
sidered dangerous  in  any  amount,  though  it 
appears  that  zinc  and  copper,  being  least  cumu- 
lative, are  rather  less  objectionable  in  minute 
amount  than  the  others.  Concerning  the  limit 
of  safety  with  manganese  and  chromium  very 
little  is  known,  but  their  presence  in  appreciable 
quantity  must  be  looked  upon  with  suspicion. 

Chlorids  and  Phosphates. — Chlorids — prin- 
cipally sodium  chlorid — and  phosphates  are 
abundantly  distributed  in  rocks  and  soils,  and 
find  their  way  into  natural  waters;  but  while  the 
former  are  freely  soluble  and  remain  in  undi- 
minished  amount  under  all  conditions  to  which 
the  water  is  subjected,  all  but  small  amounts  of 
the  latter  are  either  precipitated  or  removed  by 
the  action  of  living  organisms.  Surface  and  sub- 
soil waters  ordinarily  contain  but  a  few  parts  per 


120  INTERPRETATION    OF    RESULTS. 

million.  Both  chlorids  and  phosphates  being 
constant  and  characteristic  ingredients  of  animal 
excretions,  it  is  obvious  that  an  excess  of  them  in 
natural  waters,  unless  otherwise  accounted  for, 
will  suggest  direct  contamination.  Proximity 
to  localities  in  which  sodium  chlorid  is  abun- 
dant, such  as  the  sea-  or  salt-deposits,  will  deprive 
the  figure  for  the  chlorin  of  diagnostic  value,  nor 
can  any  indication  of  sewage  or  other  dangerous 
pollution  be  inferred  from  high  proportion  of 
chlorin  in  deep  waters.  Further,  it  has  been 
shown  that  the  proportion  of  chlorin  in  uncon- 
taminated  waters  is  tolerably  constant,  while 
in  water  subjected  to  the  infiltration  of  sewage  the 
chlorin  undergoes  marked  variation  in  amount. 
In  most  cases,  therefore,  a  correct  judgment  can 
only  be  attained  by  comparison  with  the  average 
character  of  the  waters  of  the  same  type  in  the  dis- 
trict, and  by  examination  at  intervals  of  the  water 
in  question. 

As  regards  phosphates,  Hehner,  who  has  pub- 
lished a  series  of  analyses,  states  that  the  presence 
of  more  than  0.6  part  per  million — calculated  as 
PO4 — should  be  regarded  with  suspicion.  On  the 
other  hand,  the  absence  of  phosphates  affords  no 
positive  proof  of  the  freedom  from  pollution. 
Woodman,  who  has  carefully  investigated  this 
question,  regards  Hehner 's  limit  as  too  strict. 
He  would  fix  i  part  per  million  as  the  minimum. 


SANITARY   APPLICATIONS.  121 

He  regards  this  datum  as  valuable  in  judging  of 
the  sanitary  quality  of  the  sample. 

Nitrogen  from  Ammonium  Compounds  ("Free 
Ammonia ' ') . — Ammonium  comp  ounds  are  usually 
the  results  of  the  putrefactive  fermentation  of 
nitrogenous  organic  matter;  they  may  also  be  the 
product  of  the  reduction  of  nitrites  and  nitrates 
in  presence  of  excess  of  organic  matter.  In 
either  case,  therefore,  they  suggest  contamination. 
Deep  waters  often  contain  an  excess  of  ammonium 
compounds,  derived,  in  large  part,  from  the  re- 
duction of  nitrates.  Their  presence  here  is 
hardly  ground  for  adverse  judgment,  since  the 
water,  even  though  originally  contaminated,  has 
undergone  extensive  filtration  and  oxidation,  its 
organic  matter  converted  into  bodies  presumably 
harmless,  and  microbes  have  perished.  Such 
waters,  indeed,  usually  show  only  traces  of  un- 
changed organic  matter. 

Rain  water  often  contains  large  proportions 
of  ammonium  compounds;  but  here,  also,  the 
fact  can  not  condemn  the  water,  since  it  does  not 
indicate  contamination  with  dangerous  organic 
matter. 

The  evolution  of  ammonia  in  the  distillation 
of  rain  water  may  continue  indefinitely,  the  larger 
portion  passing  over  in  the  first  distillates,  but 
small  quantities  being  present  even  after  the 
distillation  has  been  much  prolonged.  The  same 


122       INTERPRETATION  OF  RESULTS. 

continuous  evolution  of  ammonia  has  been  noted 
in  waters  containing  urea,  but  in  this  case  a  larger 
proportion  is  collected  in  the  earlier  distillates, 
nearly  all  coming  over  before  one-half  the  water 
has  been  distilled. 

Nitrogen  by  Alkaline  Permanganate  ("Albumi- 
noid Ammonia"). — A  large  yield  of  ammonia 
by  boiling  with  alkaline  potassium  permanganate 
will,  of  course,  point  to  an  excess  of  nitrogenous 
organic  matter.  The  inferences  to  be  drawn 
depend  upon  the  origin  and  condition  of  the  or- 
ganic material.  If  animal,  the  water  may  at 
once  be  condemned  as  unsafe.  Waters  contain- 
ing excessive  amounts  even  of  vegetable  matter 
are  not  free  from  objection,  since  they  have  fre- 
quently caused  persistent  diarrhea .  If  the  organic 
matter,  whether  animal  or  vegetable,  is  in  a  state 
of  active  decomposition,  it  is  doubly  objection- 
able. Mallet  has  called  attention  to  the  fact 
that  such  waters,  as  a  rule,  yield  ammonia 
rapidly,  whereas  non-decomposing  material 
yields  it  but  slowly,  and  he  points  out  the  im- 
portance, therefore,  of  noting  the  rate  at  which 
the  ammonia  collects  in  the  distillate. 

Smart  has  observed  that  water  containing 
fermenting  vegetable  matter  is  colored  yellow 
by  boiling  with  sodium  carbonate. 

Inferences  as  to  the  source  of  the  organic 
matter  can  usually  be  drawn  from  the  amount  of 


SANITARY    APPLICATIONS.  123 

chlorin  and  nitrates  present.  If  the  chlorin  is 
high — i.  e.,  in  excess  of  the  average  of  the  dis- 
trict— it  may  be  inferred  that  the  material 
is,  in  great  part,  of  animal  origin.  In  this  case 
the  nitrates  will  either  be  high  or  entirely  absent, 
according  as  the  contaminating  matter  has 
passed  through  soil  or  enters  the  water  directly. 

A  large  amount  of  vegetable  matter  will,  as 
a  rule,  show  itself  by  the  color  it  imparts  to  the 
water. 

Total  Nitrogen. — Drown  and  Martin's  re- 
sults with  surface  waters  indicate  that  the  total 
nitrogen  obtained  by  their  process  is  about 
twice  that  obtained  by  alkaline  permanganate. 
The  experiments  made  by  Leffmann  and  Beam 
accord  with  this.  Further  observation  on  dif- 
ferent waters  and  by  different  observers  will  be 
required  to  determine  the  value  to  be  assigned 
to  the  figures  obtained  by  this  method.  This 
method  is  especially  suitable  for  studying  the 
effects  of  filtration,  storage,  etc.,  on  the  nitroge- 
nous organic  matter  in  water. 

Nitrogen  as  Nitrites. — Nitrites  are  present  in 
water  as  the  result  either  of  incomplete  nitrifi- 
cation of  ammonium,  or  the  reduction  of  al- 
ready formed  nitrates,  under  the  influence  of 
reducing  agents  or  microbes.  Since  they  are 
transition  products,  their  presence  in  water  is 
usually  evidence  of  existing  fermentative  changes, 


124  INTERPRETATION    OF    RESULTS. 

and,  further,  may  be  taken  as  indicating  that  the 
water  is  unable  to  dispose  of  the  organic  con- 
tamination. When,  however,  the  conditions  are 
such  that  oxidation  can  not  take  place,  nitrites 
may  persist  for  a  long  time.  This  sometimes 
occurs  in  deep  waters  in  which  fermentative 
changes  have  long  since  ceased,  but  oxygen  is 
not  available.  These  contain  not  infrequently 
small  amounts  of  nitrites,  to  which  the  same  de- 
gree of  suspicion  can  not  be  attached.  When 
nitrites  are  found  in  these  waters,  the  possibility 
of  their  introduction  from  polluted  subsoil  water, 
through  defective  tubing,  must  not  be  overlooked. 
Rain  water,  also,  sometimes  contains  nitrites  de- 
rived from  the  air,  and  therefore  not  indicative 
of  any  putrefactive  change.  The  presence  of 
measurable  quantities  of  nitrites  in  river  or  sub- 
soil water  is  sufficient  ground  for  condemnation. 
Nitrogen  as  Nitrates. — Nitrates  are  the  final 
point  in  the  oxidation  of  nitrogenous  organic 
matter,  especially  animal  matters.  Rain  water 
and  that  from  mountain  streams  and  deep  wells, 
except  from  cretaceous  strata,  generally  con- 
tains only  traces,  but  river  and  subsoil  waters 
will  always  contain  appreciable  amounts,  unless 
some  reducing  action,  such  as  recent  sewage 
pollution,  is  at  work.  When,  therefore,  a  water 
contains  enough  mineral  matter  to  demonstrate 
its  percolation  through  soil,  and  at  the  same  time 


SANITARY    APPLICATIONS. 

is  free  from  nitrates  or  contains  only  traces,  the 
occurrence  of  a  destructive  fermentation  may  be 
inferred.  These  cases  are  not  uncommon  among 
well-waters,  and  the  samples  are  generally  turbid 
from  suspended  organic  matter.  Decided  de- 
parture, either  by  increase  or  decrease,  from 
the  proportion  of  nitrates  usual  in  the  same 
class  of  water  in  any  district  may  be  taken  as 
evidence  of  contamination. 

Oxygen-consuming  Power. — Sanitary  authori- 
ties differ  very  much  as  to  the  significance  of 
this  datum.  Attempts  have  been  made  to  fix 
maximum  limits  for  the  various  types  of  water, 
and  also  to  gage  the  character  and  condition  of 
the  organic  matter  by  observing  the  rate  at 
which  the  oxidation  takes  place,  but  no  positive 
conclusions  can  be  given.  In  general,  it  may 
be  said  that  a  sample  which  has  high  oxygen- 
consuming  power  will  be  more  likely  to  be  un- 
wholesome than  one  which  is  low  in  this  respect ; 
but  the  interferences  are  so  numerous,  and  the 
susceptibility  to  oxidation  of  different  organic 
matters,  of  even  the  same  type,  is  so  different, 
that  the  method  is  at  best  only  of  accessory 
value.  It  is  especially  suitable  for  consecutive 
determinations  on  the  same  supply. 

For  the  method  with  acidified  permanganate 
at  the  boiling  heat,  the  German  chemists,  who 
employ  it  largely,  regard  an  absorption  of  2.5 


126       INTERPRETATION  OF  RESULTS. 

parts  of  oxygen  per  million  as  suspicious,  and  some 
sanitary  authorities  have  fixed  3.8  parts  of 
oxygen  per  million  as  the  highest  permissible 
limit. 

Dissolved  Oxygen. — Full  aeration  of  water  is 
favorable  to  the  destruction  of  organic  matter; 
a  decided  diminution  in  the  quantity  of  dissolved 
oxygen  may  show  excess  of  such  matter  and  of 
microbic  life.  Gerardin  has  pointed  out  that 
this  diminution  is  associated  with  the  develop- 
ment of  low  forms  of  vegetable  life,  and  Leeds  has 
recorded  similar  facts.  These  changes  are  more 
likely  to  take  place  in  still  waters,  and  are  fre- 
quently accompanied  by  disagreeable  odor  and 
taste.  In  cases  in  which  stored  waters  become 
unpalatable,  these  facts  should  be  borne  in  mind. 

Hardness. — The  degree  of  hardness,  unless 
very  high,  has  but  little  bearing  on  the  sanitary 
value  of  water,  but  is  important  in  reference  to  its 
use  for  general  household  purposes,  in  view  of  the 
soap-destroying  power  which  hard  waters  possess. 

USUAL  ANALYTIC  RESULTS  FROM  UNCONTAMI- 
NATED  WATERS. 

Milligrams  per  Liter. 
RAIN.  SURFACE.        SUBSOIL.  DEEP. 

Total  solids, 5  to  20         15  upward      30  upward         45  upward 

Chlorin, Traces  to  i         i  to  10  2  to  12        Traces  to  large 

quantity 
Nitrogen  by  per-  0.08  to  0.20  0.05  to  0.15  o. 05100.10      0.03  too.io 

manganate. 

Nitrogen  as  NH<  0.20  to  0.50  o.ootoo.os  o.ootoo.oa  Generally  high 
Nitrogen  as  ni-  None  or  None  None  None  or  traces 

trites.  traces 

Nitrogen    as    ni-       Traces       0.75101.25       1.5  to  5  o.ootoa 

trates. 


SANITARY   APPLICATIONS.  127 

Inferences  from  Cultures. — It  is  obviously 
impossible  to  fix  a  rational  limit  to  the  number 
of  microbes  (points  of  microbic  life)  permissible 
in  a  given  sample,  since  season,  temperature,  ex- 
tent of  exposure  to  air  and  the  time  during  which 
the  sample  has  remained  at  a  given  temperature 
affect  the  development  materially.  Below  a  few 
meters  from  the  surface,  the  soil  is  generally 
almost  sterile,  hence  subsoil  waters  deriving  their 
supply  from  highly  polluted  sources  may  show 
but  few  microbes.  Deep- well  water  is  generally 
sterile.  Rain  water  is  usually  rich  in  microbes, 
surface  water  extremely  variable. 

In  addition,  media  made  with  great  care  by 
different  persons  and  with  materials  from  different 
sources  will  show  differences  with  the  same 
sample.  Many  bacteriologists  have  fixed  a  limit 
of  100  living  organisms  to  i  c.c.  This  is  ob- 
viously largely  the  influence  of  the  number  it- 
self, round  and  somewhat  imposing,  but  it  has 
been  made  the  standard  by  the  U.  S.  Public 
Health  Service  which,  in  controlling  water-sup- 
plies coming  within  the  interstate  powers  of  the 
Federal  Government,  has  ruled  that  waters 
yielding  more  than  100  colonies  per  c.c.  in 
standard  agar  at  37°  for  twenty-four  hours 
(see  page  102)  are  not  safe;  that  not  more  than 
one  in  five  tubes  incubating  10  c.c.  of  the  sample  in 
lactose-peptone-broth  shall  show  appreciable  gas 


128       INTERPRETATION  OF  RESULTS. 

in  forty-eight  hours;  that  cultivation  in  litmus- 
lactose-agar  or  Endo's  medium  for  twenty- 
four  hours  at  37°  shall  not  show  red  colonies. 
Further,  when  typical  colonies  from  these  agar- 
cultures  are  re-inoculated  in  lactose-peptone- 
broth,  not  more  than  10  per  cent,  of  the  tube 
shall  be  occupied  with  gas  after  forty-eight  hours 
at  37°. 

Culture  methods  have  special  value  in  the 
examination  of  subsoil  waters,  and  in  deter- 
mining the  efficiency  of  systems  of  purification, 
being,  far  as  the  latter  purpose  is  concerned, 
indispensable. 

PURIFICATION  OF  WATER. 

Drinking  Water. — The  most  obvious  method 
of  purifying  water  is  by  distillation,  but  the  process 
is  too  expensive  for  general  use.  It  has  been  used 
for  supplying  vessels  at  sea  and  in  tropic  localities 
in  which  the  natural  waters  may  be  contami- 
nated with  malarial  or  other  germs.  The  ma- 
jority of  microbes  are  killed  by  short  exposure 
to  a  temperature  of  100°;  hence,  water  may  be 
purified,  on  a  small  scale,  by  simple  boiling. 
Freezing  does  not  have  as  beneficial  an  effect, 
many  microbes  retaining  vitality  for  a  long  time 
in  ice,  and  even  at  very  low  temperatures.  For 
household  purposes  filters  are  in  use,  the  most 
efficient  being  those  in  which  the  water  passes 


PURIFICATION   OF    WATER.  1 29 

through  the  pores  of  unglazed  porcelain.  Even 
these,  however,  should  be  frequently  cleaned  or 
they  will  deliver  a  contaminated  filtrate. 

The  purification  of  water  on  the  large  scale  for 
either  household  or  industrial  purposes  is  an 
engineering  problem,  the  details  of  which  are 
not  within  the  scope  of  this  work.  Several 
types  of  methods  have  been  devised.  One 
type  depends  on  adding  to  the  water  substances 
that  produce  colloidal  precipitates,  that  entangle 
the  suspended  matters,  living  and  non-living,  and, 
by  making  them  more  bulky,  permit  of  re- 
moval by  rapid  filtration  under  pressure.  Alumi- 
num compounds,  e.  g.,  aluminum  sulfate,  are 
mostly  used.  In  most  cases  sufficient  carbon- 
ates are  present  in  the  water  to  react,  producing 
aluminum  hydroxid,  a  colloidal  mass  that  has 
attraction  for  many  of  the  suspended  matters, 
and  even  for  some  of  the  dissolved  matters.  If 
the  water  is  low  in  carbonates,  small  amounts  of 
lime  may  be  added  and  the  result  will  be  obtained. 

Filtration  through  porous  materials,  generally 
fine  sand,  at  a  slow  rate  permits  of  a  biologic 
action — the  growth  of  microbes  in  the  upper 
layers  of  the  sand  by  which  the  food  of  the 
microbes  is  exhausted  and  they  perish.  This 
is  the  preferred  method  for  large-scale  supplies. 

It  has  been  found  advantageous  in  many  cases 
to  supplement  the  action  of  the  filter  by  in- 
9 


130       INTERPRETATION  OP  RESULTS. 

troducing  small  amounts  of  germicides  into 
the  water  before  delivery  to  the  distributing 
system.  Many  substances  have  been  tried. 
One  of  the  most  efficient  is  ozone,  but  it  is 
costly  to  prepare  and  difficult  to  mix  with  the 
water.  At  present  the  preferred  substance  is 
chlorin,  introduced  either  in  free  state  or  in  the 
form  of  the  so-called  "chlorid  of  lime,"  generally 
termed  by  chemists  calcium  hypochlorite,  but 
even  this  name  is  not  unchallenged.  The  article 
is  cheap  and  of  fairly  constant  quantity,  the  best 
commercial  samples  being  capable  of  yielding 
about  one-third  their  weight  of  chlorin.  Very- 
small  amounts  of  chlorin  suffice  to  kill  all  ordi- 
nary water  microbes,  and  the  use  of  this  agent 
is  now  much  in  favor. 

Purification  of  boiler  waters  is  directed  princi- 
pally to  diminishing  corrosion  and  preventing 
scale.  The  former  problem  is  discussed  on  pages 
84,  85;  the  latter  relates  principally  to  the  re- 
moval of  the  calcium  carbonate  and  sulfate, 
magnesium  carbonate  and  chlorid.  Both  car- 
bonates are  appreciably  soluble  in  pure  water. 
The  ratio  of  15  parts  of  calcium  carbonate  per 
1,000,000  is  usually  stated  to  be  the  solubility, 
but  Allen  found  that  solutions  can  be  obtained 
containing  twice  this  amount.  If  the  water 
contains  carbonic  acid,  it  will  take  up  a  much 
greater  proportion  of  the  carbonates,  but  in 


PURIFICATION    OF   WATER.  131 

this  case  they  will  be  deposited  from  the  solution 
by  boiling.  This  has  been  accounted  for  by 
supposing  the  existence  of  soluble  bicarbonates, 
which  are  decomposed  by  the  boiling.  Nearly 
all  of  these  carbonates  can  be  thrown  out  of  solu- 
tion by  any  means  that  will  deprive  the  water  of 
the  carbonic  acid.  Sodium  hydroxid  is  often 
employed  for  the  purpose,  and  should  be  added 
in  quantity  just  sufficient  to  form  normal  sodium 
carbonate.  If  there  are  present  in  the  water 
calcium  and  magnesium  chlorids  and  sulfates, 
these  also  will  be  decomposed  and  precipitated 
by  the  sodium  carbonate  so  formed.  If  the 
amount  of  sodium  carbonate  formed  is  not 
sufficient  to  decompose  all  of  these  bodies,  a 
sufficient  quantity  should  be  added  with  tbe 
sodium  hydroxid  to  effect  the  complete  decom- 
position. The  precipitate  is  allowed  to  settle 
or  filtered  off. 

In  cases  in  which  the  feed- water  is  heated  be- 
fore it  enters  the  boiler,  it  may  only  be  necessary 
to  add  to  the  water  sodium  carbonate  in  quantity 
sufficient  to  decompose  the  calcium  and  mag- 
nesium chlorids  and  sulfates,  since  the  heat  alone 
will  suffice  to  throw  down  the  carbonates. 

Care  should  be  taken  in  these  precipitations 
that  no  more  sodium  hydroxid  is  added  than  is 
required  for  the  precipitation,  since  excess  pro- 
duces corrosion. 


132       INTERPRETATION  OP  RESULTS. 

Soluble  phosphates  added  to  a  water  precipi- 
tate completely  in  a  flocculent  condition  any  cal- 
cium, magnesium,  iron,  or  aluminum.  This  re- 
action can  be  best  applied  by  using  the  commercial 
trisodium  phosphate.  By  reason  of  the  facility 
with  which  this  substance  loses  a  portion  of  its 
sodium  to  acids,  it  acts  not  only  as  a  precipitant 
to  the  above  materials,  but  will  neutralize  any 
free  mineral  acid  present  in  the  water.  From 
evidence  submitted  by  those  who  have  used  the 
process  on  the  large  scale,  it  appears  that  not 
only  is  no  hard  scale  formed,  but  that  scale 
already  existing  prior  to  its  use  is  gradually  dis- 
integrated and  removed  with  the  sludge.  Ex- 
periments indicate  that  no  injury  results  from 
an  excess  of  the  material;  but  the  economical 
employment  of  the  method,  especially  with  very 
hard  waters,  can  only  be  based  upon  a  correct 
analysis,  and  an  estimation  of  the  phosphate 
required  for  the  precipitation.  In  many  cases 
the  composition  of  the  water  will  be  such  that  a 
partial  precipitation  will  be  sufficient. 

Considerable  success  has  been  obtained  by  the 
use  of  fluorids  as  precipitants  of  scale-forming 
elements.  Sodium  aluminate  has  also  been 
recommended.  A  preparation  termed  "permu- 
tite"  made  by  fusing  together  kaolin,  quartz  and 
sodium  carbonate  is  being  much  used. 

Waters  rich  in  ferrous  compounds   may   be 


IDENTIFICATION  OF  THE  SOURCE  OF  WATER.  133 

purified  by  thorough  aeration  and  filtration,  the 
iron  precipitating  as  ferric  hydroxid. 


IDENTIFICATION  OF  THE  SOURCE  OF 
WATER. 

The  determination  of  the  course  of  underground 
streams,  and  of  communications  between  col- 
lections of  water,  is  often  an  important  practical 
problem.  In  geologic  and  sanitary  surveys, 
valuable  information  may  occasionally  be  gained. 
The  method  generally  pursued  when  connection 
between  water  at  accessible  points  is  to  be  de- 
tected, is  to  introduce  at  one  point  some  substance 
not  naturally  existing  in  the  water,  and  capable 
of  recognition  in  small  amount.  Lithium  com- 
pounds are  among  the  best  for  this  purpose. 
They  are  not  frequent  ingredients  of  natural 
waters,  and  are  easily  recognized  by  the  spectro- 
scope. Lithium  chlorid  is  the  most  suitable. 
The  quantity  to  be  employed  will  vary  with  cir- 
cumstances. It  scarcely  needs  to  be  stated  that 
the  waters  under  examination  should  be  carefully 
tested  for  lithium  before  using  the  method. 

When  the  lithium  method  is  inadmissible,  re- 
course must  be  had  to  other  substances  of  dis- 
tinct character,  such  as  strontium  chlorid,  but 
this  possesses  the  disadvantage  that  a  con- 
siderable amount  may  be  rendered  insoluble, 


134       INTERPRETATION  OF  RESULTS. 

and  thus  lost  in  the  ordinary  transit  through  soil. 
Use  has  been  made  of  organic  coloring  matters 
of  high  tinctorial  power,  one  of  the  most  suit- 
able of  which  is  fluorescein.  This  will  communi- 
cate a  characteristic  and  intense  fluorescence  to 
many  thousand  times  its  weight  of  water.  The 
coloration  is  distinct  only  in  alkaline  liquids. 
Other  colors,  such  as  anilin-red,  may  be  employed. 

Vandenburgh  made  successful  use  of  both 
methods  in  a  suit  growing  out  of  use  of  a  creek 
for  the  supply  of  Syracuse,  N.  Y.  It  was  shown 
that  the  creek  supplied  a  spring  which  was  used 
by  a  manufacturing  establishment. 

A  more  important  feature  of  the  problem  from 
a  sanitary  point  of  view  is  the  determination  of 
the  source  of  a  given  current  or  collection  of 
water,  when  such  source  is  inaccessible.  Prob- 
lems of  this  character  are  not  infrequent  in  large 
cities  in  which  the  systems  of  water-supply  and 
drainage  are  defective,  thus  giving  occasion  to 
accumulations  of  water  in  cellars  and  similar 
places.  Often,  in  these  cases,  no  extended  ex- 
plorations can  be  made,  by  reason  of  the  adja- 
cent buildings  and  conflicting  property  interests, 
and  the  question  may  arise  whether  the  water 
proceeds  from  a  leaky  hydrant,  drain,  sewer,  or 
subsoil  current.  It  is  obvious  that  in  the  case  of 
the  collection  of  water  in  a  cellar  from  causes 
other  than  surface  washings  or  entrance  of  rain, 


IDENTIFICATION  OF  THE  SOURCE  OF  WATER.  135 

it  must  have  passed  through  some  distance  of 
soil,  and  in  built-up  districts  will  almost  certainly 
be  charged  with  organic  refuse.  To  correctly 
interpret  the  results,  it  will  be  necessary  to  know 
the  general  character  of  the  subsoil  water  of 
the  district  and  the  composition  of  the  public 
supply.  As  a  rule,  the  transmission  of  water 
through  moderate  distances  of  soil  will  not 
materially  increase  the  mineral  constituents. 
Hence,  if  the  sample  contains  an  excess  of  dis- 
solved matters  as  compared  with  the  water- 
supply  of  the  district,  it  may  reasonably  be  in- 
ferred that  it  is  derived  from  a  drain,  sewer,  or 
subsoil  current.  In  these  investigations  it  will 
generally  be  sufficient  to  determine  the  total 
solids,  odor  on  heating,  chlorin,  nitrates,  and 
nitrites. 

Occasionally,  the  analytic  results  will  be  am- 
biguous, and  it  is  advisable  to  make  examina- 
tions of  more  than  one  sample,  since  accidental 
circumstances,  rain-fall,  etc.,  may  affect  the  com- 
position of  the  water. 

Instances  of  the  contamination  of  water  by 
unusual  substances  are  occasionally  noted,  and 
these  sometimes  afford  a  clue  to  the  source  of 
the  water.  Among  the  instances  of  this  kind 
within  the  experience  of  Dr.  Beam  and  myself, 
may  be  noted  the  contamination  with  petroleum 
and  with  soap.  In  the  former  case  it  was  evi- 


136       INTERPRETATION  OF  RESULTS. 

dent  that  the  contamination  was  from  a  leaky 
pipe  connecting  two  refineries.  In  the  latter  it 
was  shown  to  be  derived  from  an  adjoining 
building  used  as  a  laundry. 


FACTORS  FOR  CALCULATION. 


137 


FACTORS  FOR  CALCULATION. 

Parts  per 

100,000    X  0.7      =  Grains  per  Imperial  gallon 

Parts  per  i 

,000,000    X  0.07    =  Grains  per 

Imperial  gallon 

Parts  per 

100,000    X  0.583  =  Grains  per 

U.  S.  gallon 

Parts  per  i 

,000,000    X  0.058  =  Grains  per 

U.  S.  gallon 

Grains  per 

Imp.  gal.  -f-  0.7      =  Parts  per 

100,000 

Grains  per 

Imp.  gal.  -5-  0.07    =  Parts  per  i 

,000,000 

Grains  per 

U.  S.  gal.  4-  0.583  =  Parts  per 

100,000 

Grains  per 

U.S.  gal.  -r-  0.058  =  Parts  per  1,000,000 

A12O3        X  0.53    =  Al 

AgCl         X  0.247  =  Cl 

BaSO4       X  0.588  =  Ba 

BaSO4      X  0.41  1  =  SO4 

( 

BaSO4      X  0.342  =  SO3 

CaO         X  0.715  =  Ca 

CaO         X  1.78    =  CaCO3 

CaCO3      X  0.4      =  Ca 

Cl             X  1.64    =  NaCl 

Fe2O3        X  0.7      =  Fe 

KC1          X  0.525  =  K 

K2PtCl6     X  0.16    =  K 

K2PtCl8    X  0.306  =  KC1 

Mg2P2O7  X  0.218  =  Mg 

Mg2P2O7  X  0.854  =  PO4 

Mg2P2O7  X  0.757  =  MgCO3 

MnS         X  0.633  =  Mn 

NaCl         x  0.394  =  Na 

N              X  4.42    =  NO3 

N              X  3-27    =  NO2 

N              X  1.22    =  NH3 

NH3          X  0.823  =  N 

138       INTERPRETATION  OF  RESULTS. 


ATOMIC  WEIGHTS. 

Expressed  to  nearest  first  decimal . 

Aluminum 27.1             Magnesium 24.3 

Barium 137.4            Manganese 54.9 

Calcium 40.1             Nitrogen 14.0 

Carbon 12.0            Oxygen 16.0 

Chlorin1 35.5            Phosphorus 31.0 

Chromium 52.0            Platinum 195.2 

Copper 63.6            Potassium 39.1 

Hydrogen1 i.o            Silver 107.9 

lodin 126.9            Sodium 23.1 

Iron 55.9            Sulfur 32.  o 

Lead 207.1            Zinc 65.4 

Lithium 7.0 

1  More  accurately,  35.46  and  1.008,  respectively. 


INDEX. 


Acidity,  determination  of,  16. 
Action  of  water  on  metals,  79- 
Aeration  of  water,  126. 
Agar,  97. 

Albuminoid  ammonia,  22,  122. 
Alkali  carbonates,  50. 
Alkaline  permanganate,  26. 
Alum,  action  of,  121. 

,  test  for,  60. 

,  use  of,  127. 

Aluminum,  determination  of,  64. 

test  for,  6a. 

Ammonia,  albuminoid,  22,  122. 

,  free,  22,  31,  122. 

,  free  water,  25. 

,  process,  22. 

Ammonium  chlorid,  standard,  25. 

molybdate,  41. 

Analysis,  statement  cf,  114. 
Arsenic,  detection  of,  57. 
Artesian  water,  i,  126. 
Atomic  weights,  138. 

Bacillus  typhosus,  1 13. 

coli  communis,  113. 

Bacteriologic  examinations,  10,  89, 

94. 

Barium,  detection  of,  56. 
Bile-media,  103. 
Biologic  examinations,  89. 
Boiler  scale,  75. 

water,  84. 

; ~,  purification  of,  134. 

Boric  acid,  detection  of,  75. 
Bottle-culture,  96. 
Bouillon,  98. 
Broth,  98. 

Calcium,  determination  of,  65. 

removal  of,  132. 

sulf  ate  in  boiler  water,  86. 

Carbonic  acid,  determination  of, 

Chlorin,  determination  of,  20. 

,  significance  of,  119. 

Chromium,  detection  of,  56. 
Clarifying  water,  128. 
Collection  of  samples,  8. 
Color,  determination  of,  n. 

,  significance  of,  117. 

Conversion  of  ratios,  137. 
Copper,  detection  of,  62. 

,  determination  of,  62. 

Corrosion  of  boilers,  83. 
Culture-media,  98,  102. 

inferences,  127. 

procedures,  107. 

Deep  water,  I,  126. 


Demijohn  for  samples,  8. 
Denitrification,  5. 
Distilling  apparatus,  24. 

Endo  medium,  104. 
Esculin  medium,  105. 

Fermentation,  100,  122. 
Filters,  129. 
Filtration,  129. 
Fluorescein,  use  of,  134. 

Gallon,  imperial,  114,  137. 

,  U.  S.,  114,  137. 

Gelatin,  97. 

Ground  water,  i,  126. 

Hardness,  degrees  of,  54. 

,  non-carbonate,  48,  149. 

,  permanent,  48,  149. 

,  significance  of,  126. 

,  temporary,  48. 

Hard  scale,  85. 

water,  softening  of,  130. 

Hesse-agar,  103. 

Hydrogen  sulfid,  determination  of, 
72. 

Identification  of  source,  133. 
Indol  reaction,  106. 
Interpretation  of  results,  114. 
Iron,  determination  of,  58,  64. 
,  significance  of,  119. 

Kolle's  flask,  96. 

Lactose-media,  101,  103.       ^ 
Lead,  action  of  water  on,  81. 

,  detection  of,  61. 

,  significance  of,  80. 

Lithium,  detection  of,  77. 

,  determination  of,  71. 

Litmus-agar,  101. 
milk,  103. 

Magnesia  in  sludge,  85. 
Magnesium  determination  of,  66. 

chlorid,  effects  of,  84. 

Manganese,  detection  of,  59. 

,  determination  of,  64. 

Meat-extract,  97. 
Micro-filter,  92. 

Nessler  reagent,  26. 

Nesslerizing,  28. 

Nitrates,  determination  of,  32. 

,  fprmation  of,  5. 

,  significance  of,  124. 

Nitrification,  5. 


139 


140 


INDEX. 


Nitrites,  determination  of,  35. 

,  f9rmation  of,  5. 

,  significance  of,  123. 

Nitrogen  as  ammonium,   22,   31, 

122. 

nitrates,  32,  124. 

nitrites,  35,  123. 

by  permanganate,  22,  122. 

total  organic,  31,  123. 

Odor  in  water,  12. 

from  residue,  19. 

significance  of ,  117. 

Organic  matter,  test  for,  39. 
Oxygen-consuming  power,  37,  125. 
dissolved,  42,  126. 

Permanganate  method,  39. 
Peptone,  9. 
Petri-dish,  96. 
Phenoldisulfonic  acid,  33. 
Phosphates,  determination  of,  40. 

significance  of,  1 19. 

Poisonous  metals,  55,  119. 
Potassium,  determination  of,  67. 
Pumice,  26. 

Pure  water,  corrosion  by,  83. 
Purification  of  boiler  water,  130. 
drinking  water,  128. 

Rain  water,  i,  126. 
Reaction,  15. 


of  media,  99. 


Results,  statement  of,  114. 
River  water,  i,  126. 

Samples,  collection  of,  8. 
Scale,  85. 

— ,  analysis  of,  75. 

Silica,  determination  of,  63. 

Silver-test  for  organic  matter,  39. 

Sludge,  85. 

Soap  solution,  52. 

Sodium,  determination  of,  67. 

Solids,  total,  significance  of,  118. 

,  determination  of,  16. 

Source  tracing,  133. 
Specific  gravity,  78. 
Spectroscopy,  76. 
Starch  indicator,  44. 
Statement  of  analysis,  114. 
Subsoil  water,  i,  126. 
Sulfates,  determination  of,  67. 
Sulfids,  determination  of,  72. 
Surface  water,  i,  126. 

Taste,  significance  of,  117. 
Total  organic  nitrogen,  29. 

solids,  16. 

,  significance  of,  118. 

Turbidity,  13,  117. 

Zinc,  detection  of,  56. 


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